List of checkpoints to cross the border to Argentina
To exit to Chile there is a first stop where they give the driver a piece of paper saying how many people are in the vehicule. If you are not going to go all the way with the same driver don't forget to ask for a specific piece that say you are crossing on foot or something. Also drivers can be reluctant to pick you up all the way through the border so a sign sayin' Frontera or Aduana might help (then you can speak with them in the car).
If you are going to Chile: it is forbidden to enter with any kind of organic stuff such as fruits, veggies, beans, seeds, cheese, etc you can try to pass them in your pockets. Just be sure to declare that you are passing with some organic stuff (rice, mate, polenta) so they can't charge you for lying and play dumb if you get caught. Worked for me with one bag of pine nuts (piñones) and one bag of seeds.
You can also only bring 2 packs of cigarettes, since they are much more expensive in Chile, or smuggle more.
In the north, most of the trucks will not pick you up because are afraid that Gendarmes can complains, eazy took a lift from a local truck and asked the driver to stop a Paraguayan truck for him.
Chilean Border Crossings North to South
The following is a list of all the major border crossings between Argentina and Chile, sorted out by Mind of a Hitchhiker and ordered from north to south. Not all of these have been hitchhiked by HitchWiki contributors. As most of them cross the Andes mountain range, not all of them stay open year round. Some might be hitchable in summer during the tourist season, but not outside that. Do your research before you cross! This was the disclaimer.
Paso Jama is the northernmost pass across the andes from San Pedro, CL to Juyjuy, AR. Coming from Chile, Keith had to have his pack x-rayed. There are lots of Paraguayan trucks passing through here and few civillians. Keith waited 1.5 hours in San Pedro and 2 hours at the border. The border is at 4200m and can be extremely windy and cold, especially at night - be prepared! The immigration building on the Argentinian side is at the end of town. Crossing from Jujuy province into Region II de Antofagasta.
Paso Sico on the Argentinian Ruta 51, nearest Argentinian hamlet is named Catua. From Jujuy province into Region II de Antofagasta. Let us know if you hitchhiked this.
Paso Socompa on the Argentinian Ruta 163. From Salta province to Region II de Antofagasta, next to an active volcano. Let us know if you hitchhiked this.
Paso San Francisco is between Copiapo, Chile and San Miguel, Argentina. There is little traffic along this route and you could wait for days at 3800m. Not recommended. Located on the Ruta 60. Crosses from Catamarca province into Region III de Atacama.
Paso Pircas Negras on the Ruta 76. From La Rioja province to Region III de Atacama. Let us know if you hitchhiked this.
Paso de Agua Negra on the Ruta 150. The customs office is near Las Flores 90km away. Crosses from San Juan province into Region IV de Coquimbo. Mind of a Hitchhiker got offered a ride from Rodeo and took it. This is the highest border crossing between the two countries, with a maximum altitude of 4.780 meters. A large chunk of the 180 km between border checks is unpaved, but with all the glaciers, it's one of the most spectacular routes across the Andes out there. The Chilean side is called Juntas del Toro and the nearest town city is La Serena. It's only open from December to April, and might close on other days as well due to bad weather. Read Las Flores on how to do it.
Paso Internacional Los Libertadores between Mendoza and Santiago de Chile is probably the best option with lots of truck and civilian traffic. You will also pass Mt. Aconcagua, the tallest mountain in the Southern and Western hemispheres. There's a tunnel between the two countries. Goes between Mendoza province and Region V de Valparaiso.
Paso Vergara on the Ruta 226. Crosses from Mendoza province to Region VII del Maule. Argentinian customs is 8km from the actual border. Let us know if you hitched this.
Paso Pehuenche on the Ruta 145. Crosses from Mendoza province to Region VII del Maule. Migration is in Las Loicas, 40 km from the actual border. Let us know if you hitched this.
Paso Pichachen on the Ruta 6. Crosses from Neuquen province to Region VIII del Bio Bio. Let us know if you hitched this.
Paso Pino Hachado on the Ruta 242. Crosses from Neuquen province to Region IX de la Araucania. Argentinian immigration is 2,5km from the actual border. Let us know if you hitched this.
Paso Icalma on the Ruta 13. Crosses from Neuquen province to Region IX de la Araucania. Argentinian immigration is 6km from the actual border. Let us know if you hitched this border.
Paso Mamuil Malal on the Ruta 60. Crosses from Neuquen province to Region IX de la Araucania. Argentinian immigration is 1,5km from the actual border. Let us know if you hitched this border.
Paso Carirriñe on the Ruta 62. Crosses from Neuquen province to Region XIV los Rios. Argentinian immigration is 47km from the actual border. Let us know if you hitched here.
Paso Hua Hum on the Ruta 48. Crosses from Neuquen province to Region XIV los Rios. Argentinian customs is 3km from the actual border. The Chilean one is on the actual border. In Chile you need to take a ferry to get connected to the other roads. Let us know if you hitched here.
Paso Fronterizo Cardenal Antonio Samoré on the Ruta 231. Crosses from Neuquen province to Region X de Los Lagos. The Argentinian customs is 17km from the actual border. Let us know if you hitched this one.
Paso Pérez Rosales on a Ruta with no number, from Puerto Frías in Argentina in Rio Negro province. Nearest Argentinian town of size is called Llao Llao, near Bariloche. You'll have to take several seasonal ferries in both Argentina and Chile to get here. The nearest town of size on the Chilean side is called Peulla in Region X de Los Lagos. This border is not visible on Google Maps, only on Open Street Maps. Please let us know if you accomplished this masterpiece.
Paso Futaleufú on the Ruta 259. Crosses from Chubut province to Region X de Los Lagos. The distance between the two immigration offices is less than 1km. This is a major tourist hot spot, so if the border isn't closed, it should be fairly hitchable. Please verify the hitchability once you've crossed here.
Paso Rio Encuentro on the Ruta 44. Crosses from Chubut province to Region X de Los Lagos. The Argentinian side has a town named Carrenleufú and the Chilean has one named Alto Palena. Let us know if you crossed here.
Paso Coyhaique/Coiaique on the Ruta 74. Crosses from Chubut province to Region XI Aisén del General Carlos Ibáñez del Campo. The Argentinian customs is 2km from the border and the nearest Argentinian town is named Aldea Beleiro. Let us know if you crossed here.
Paso Huemules on the Ruta 260. Crosses from Chubut province to Region XI Aisén del General Carlos Ibáñez del Campo. The Argentinian immigration office is less than 300m from the actual border and the nearest village is Lago Blanco. On the Chilean side it is 5km till the first town named Balmaceda. Let us know if you crossed this border.
Paso Palavicini on the Ruta 72 (Ruta 45 on Google Maps). Crosses from Santa Cruz province to Region XI Aisén del General Carlos Ibáñez del Campo. The Argentinian customs office is 2km from the actual border. The Chilean customs is on the limit of Puerto Ingeniero Ibáñez town as spotted by [[User:MOAH|Mind of a Hitchhiker. She took the next border. Let us know if you crossed this border.
Paso de Chile Chico on the Ruta 43. Crosses from Santa Cruz province to Region XI Aisén del General Carlos Ibáñez del Campo. The Argentinian customs office is in Los Antiguos and the Chilean one in Chile Chico. This border is perfectly hitchable, as recorded by [[User:MOAH|Mind of a Hitchhiker in a vlog. No man's land is about 8km long.
Paso Roballos on the Ruta SN near the Ruta 41. Crosses from Santa Cruz province to Region XI Aisén del General Carlos Ibáñez del Campo. The Argentinian customs office is 300 m from the actual border. The nearest village with facilities is Bajo Caracoles and oh boy, you don't want to get stuck here. Perhaps it's crossable in summer, but definitely not in winter. The nearest town in Chile is Cochrane. Let us know if you hitched this border.
Villa O'Higgins/El Chalten Foot border crossings This area is sort of the hiking capital of the continent. There's many multi-day hikes advertized in both towns. Villa O'Higgins is the last town reachable by road from the "mainland" of Chile, via the Carretera Austral/Ruta 7. You could hitchhike all the way from Arica to Santiago de Chile to Villa O'Higgins without leaving Chile - that's 4.300km. South of Villa O'Higgins, Chile splits up in a million fjords, this is where Region XII de Magallanes (y la Antarctica Chilena) begins. Chile and Argentina have disputes over what land is owned by which country. If you want to visit the southernmost region of Chile without crossing to Argentina, there's a cruise from Puerto Montt all the way to Puerto Natales and even Punta Arenas, but this won't come cheap. In El Chalten or Tres Lagos in Argentina, there's buses taking you to and from these hiking trails. One is named Paso Fronterizo Entrada Mayer on the Ruta 81. Crosses from Santa Cruz province to Region XI Aisén del General Carlos Ibáñez del Campo. Border check points are as the bird flies 12km. Rides may only be hitched from each respective main road. Permits may be needed to hike in this reserve. If you've done any border crossing in this region, please add more information.
Paso Don Guillermo on the Ruta Provincial 7. Crosses from Santa Cruz province into Region XII de Magallanes. The Argentinian customs office is 3km from the border and the Chilean one 9km, so that's 12km of no man's land. Let us know if you hitched this border crossing.
Paso Fronterizo Dorotea on the Ruta Provicial 20. Crosses from Santa Cruz province into Region XII de Magallanes. The Argentinian customs office is at a ski centre 2km from the actual border and the nearest town with facilities is Rio Turbio. Villa Dorotea is on the Chilean side with the customs office 4km from the border. Puerto Natales in Chile is nearby. Let us know if you hitched this border crossing.
Paso Laurita Casas Viejas on the Ruta 293. Crosses from Santa Cruz province into Region XII de Magallanes. The Argentinian customs office is 100m from the actual border, the Chilean one is 4km away. This is the main direct border crossing from Argentina to Puerto Natales. Let us know if you hitched this border.
Paso de Integracion Austral on the Ruta Nacional 3. Crosses from Santa Cruz province into Region XII de Magallanes. There's two buildings, but both Chilean and Argentinian customs are present in both buildings. From whichever direction you come, you always drive by the first building and get out at the second. Don't panic! At this border you can possibly expect a needlessly complicated and long process once you arrive to Argentine customs if their X-Ray machine is broken (which it often is).They must do a manual search of your bags and tend to find silly, irrelevant things like tin foil that are apparently a matter of National Security. themodernnomad was once delayed leaving Argentina at the Paso Austral to Chile for several hours because of a 'suspicion' that turned out to be baseless. Fortunately, the Gendarmeria have poorly trained attack dogs who care more about playing with towels than sniffing for contraband. The Argentinian drivers of Mind of a Hitchhiker who came driving all the way from Cordoba province to visit Ushuaia had all their apples stolen by Chilean customs, even though they crossed back into Argentina a few hours after! This was really tragic. Warn your Argentinian drivers!
Paso San Sebastián on the Ruta Nacional 3 (which casually continues on Isla Grande de Tierra del Fuego regardless of the fact that it's broken up!). Crosses from Tierra del Fuego province into Region XII de Magallanes. The Argentinian customs office is at the roundabout of the town San Sebastián, some 11km from the actual border. The Chilean customs office is 3.5km from the actual border. Use the border crossings to find direct rides to where you want to go. Argentinian plates driving into Chile will most likely drive all the way to Rio Gallegos, while Chilean plates going into Chile will likely go to Punta Arenas via the Punta Delgada ferry crossing (hitchable). To find a ride to Porvenir in Chile, Mind of a Hitchhiker asked at the Chilean customs office if anyone was going there, and got offered a ride from a guy named "El Gordo" (TheFat One) by his colleagues. His real name is Sergio, as vaguely remembered, and he drives a red Toyota Hilux. This hitchhiker gave up on trying to find an earlier ride and did crossword puzzles instead until Sergio appeared and drove her the 140km to Porvenir in no time. With excellent suspension, the ride was smooth and glorious, while driving past the Bahía Inutil (Useless Bay) chasing the imminent sunset.
Other Border Crossings on Tierra del Fuego One example may be the ferry from Ushuaia to Puerto Navarino or Puerto Williams in Chile. This little boat may only need to cross less than 10km of water in the Beagle Channel, yet costs a magical US$200 or more. There's a cruise between Puerto Williams and Punta Arenas, if you really want to visit The World's Southernmost Village, but it will probably cost you a kidney, too. Other land borders may exist between Estancia San José (Argentina) and Camerón (Chile), but as if hitchhiking isn't hard enough on the main roads of Tierra del Fuego. Kudos if you did hitch another border crossing, and again, please add information here if you did!
Some of you might need to apply for a visa or pay a reciprocity fee when entering Bolivia. It's surprisingly strict to get in. The immigration officers are not very good at making you feel welcome into their country. After filling in a form at the border, Mind of a Hitchhiker got shouted at and her form destroyed and tossed by the Bolivian immigration officer because he deemed her handwriting unreadable.
Bolivian Border Crossings West to East
Here's a list of all major border crossings between Argentina and Bolivia. One can enter Bolivia from Argentina from either the province of Salta or Jujuy. This border region has a lot of poverty, so most of them don't have fancy border complexes and paved roads, and one may have to find their entry/exit stamp very far away. Most of these border crossings are also at high altitude and some of them are not open year round. Be careful with bringing coca leafs into or from the countries. The list is not comprehensive and you are welcome to add more information.
Paso Fronterizo Villazon on the Ruta 9. The Argentinian town is called La Quiaca in Jujuy Province and the Bolivian one Villazón in Potosi Department. Immigration offices are 100m apart and the two towns are stuck together. East of this border are a few minor roads also crossing, but they don't have immigration offices, so only pursue those at your own risk. Let us know if you hitched this border.
Mecoya/Rio Santa Rosa on a side road of the Ruta 7 in Salta province. This one is not findable on Google Maps, but visible on Open Street Maps. The immigration office seems to be in the village called Santa Victoria in Argentina. You'll pass a town named Pucara de San Bernardo. Mecoya, the town on the Bolivian side, is 100km from the city of Tajira, Tajira Department, Bolivia. Let us know if you hitched this border.
Condado/La Mamora on the Ruta provincial 19 in Salta province, leading into Tajira department. Again, not findable yet on Google Maps, while Open Street Maps is pretty confident about this one. Let us know if you hitched this border.
Aguas Blancas on the Ruta provincial 50 in Salta province, leading into Tajira department. This one is bigger. Argentinian customs is 2km from the actual border. The Argentinian town of Aguas Blancas is really small, while Bermejo on the Bolivian side is rather large and has many amenities. Let us know if you hitched this border.
Paso Internacional Salvador Mazza - Yacuiba on the Ruta 34 in Salta province, leading into Tajira department. It's very big. Argentinian customs is 100m from the bridge crossing the border. The town on the Argentinian side is called Profesor Salvador Mazza and the city on the Bolivian side Yacuiba. Let us know if you hitched this border.
Paraguay is a really nice country, but immigration checkpoints are usually very far away from the border in the nearest town of size. This doesn't follow any particular logic, and sometimes one has to hitchhike more than 100km between borders on crappy roads to get the next stamp. This might result in having your exit and entry stamps not done on the same day, which might lead to nasty questions by immigration officials.
Paraguayan Border Crossings Roughly West to East
Paso Internacional Mision La Paz on a Ruta 54 in Salta province leading to Boqueron department. The nearest town of size is Santa Victoria Este/Oeste (really, they're the same town) in Argentina. On the Paraguayan side there's Pozo Hondo, but the nearest town of size is Mariscal Estigarribia some 200km away, which might be your stamp in/out point. Let us know if you hitched this border crossing.
Fortin General José Bruguez on a side road of the Ruta 86 in Formosa province, leading to Presidente Hayes department. The nearest town of size in Argentina is Villa General Manuel Belgrano. The immigration offices of both countries are 100m apart and crosses a bridge over the Rio Pilcomayo. On Google Maps, the town is abbreviated to "Fortin Gral Bruguez, Paraguay". Let us know if you hitched this border.
Puente Internacional San Ignacio de Loyola on the Ruta 11 in Formosa province, leading to Presidente Hayes department. This one is close to Asuncion, but not from the city. The Argentinian town is called Clorinda and the Paraguayan town Puerto Falcon. The nearby Paraguayan town Nanawa crosses multiple times into Clorinda, too, but lacks official exits for international passport holders. Immigration offices for both countries are 300m apart. Let us know if you hitched this border.
Puerto Pilcomayo Ferry Crossing to Ita Enramada on the Ruta Nacional A011. From Formosa province to Districto Capital department. This is a border crossing by boat into a neighborhood of Asuncion called Ita Enramada. Passport control should be 100m from the pier on the Argentinian side. Please add information about prices if you crossed borders this way.
Formosa City Ferry Crossing to Alberdi on the Ruta Nacional 11. From Formosa province to Ñeembucú department. This 600m ferry ride across the Rio Paraguay should have their respective passport controls on either side at the port at the prefectura naval. Please let us know and add information about prices if you crossed between countries here.
Colonia Cano Ferry Crossing to Pilar on Ruta 9. From Formosa province to Ñeembucú department. The nearest Argentinian town is General Lico V. Mansilla, some 40km away from the actual ferry crossing. Pilar in Paraguay is directly on the other side. Let us know about the location of the passport controls and the prices of the ferry if you take this crossing.
Ituzaingo - Ayolas Hydroelectric Dam on the Ruta 120. Passport control is about 1km before the bridge/dam starts. It's a total distance of 40km from the town of Ituzaingo in Corrientes province till Ayolas in Misiones department. Let us know if you hitched this border.
Puente Internacional San Roque González de Santa Cruz on the Ruta 105. From the Argentinian Posadas in Misiones province to the Paraguayan town Encarnacion in Itapúa Department. There's a bridge for cars, a ferry (Lancha) and even a train crossing. The passport control are on their respective sides of the bridge. Did you hitch across here? Please add more info!
San Ignacio Ferry Crossing to La Alborada near the Ruta Nacional 12 near San Ignacio, Misiones province. The ferry (Lancha) leaves from a place at the Paraná river called Puerto Nuevo, which has a camp site. This crossing is not on Google Maps, but is clearly visible on Open Street Maps. The nearest towns in Paraguay are La Alborada, Nueva Alborada and the German-sounding Hohenau in Itapúa department. Let us know if you crossed here.
Corpus Ferry Crossing to Puerto Obligado on the Ruta Provincial 6. Goes from Corpus, Misiones province, to Puerto Obligado, Itapúa department, near Bella Vista and Hohenau. Let us know if you crossed here.
Puerto Rico Ferry Crossing to Puerto Triunfo near the Ruta Nacional 12. Goes from Puerto Rico, Misiones province, to Puerto Triunfo, Itapúa department. Let us know if you crossed here.
Puerto Montecarlo Ferry Crossing to Puerto Ape Aime near the Ruta Nacional 12. Goes from Montecarlo, Misiones province, to Puerto Ape Aime, Itapúa department. Let us know if you crossed here.
Puerto Libertad Ferry Crossing to Domingo Martínez de Irala near the Ruta Nacional 12. Goes from Puerto Libertad, Misiones province, to Doningo Martínez de Irala, Alto Paraná department. Let us know if you crossed here.
Triple Frontera/Tríplice Fronteira at the end of the Ruta Nacional 12 in Puerto Iguazu, Misiones province, Argentina. From here you can cross by ferry to Paraguay, to a village named San Francisco, that is near to Ciudad del Este, Alto Paraná department. If not by ferry, one has to cross the international bridge to Brazil and then enter Paraguay. Let us know what you did around this border!
All major border crossings from Argentina to Brazil. Check whether you need a visa or not. Don't get too comfortable with your Spanish; they speak Portuguese in Brazil. Just stating the obvious here. Customs are called Alfândega in Portuguese.
Brazilian Border Crossings Roughly West to East
Triple Frontera/Tríplice Fronteira at the end of the Ruta Nacional 12 in Puerto Iguazu, Misiones province, Argentina. The town on the Brazilian side is called Foz do Iguaçu, in State of Paraná. The passport control in Argentina is 2km away from the actual border on a bridge in the Rio Iguazú/ Rio Iguaçu. The Brazilian customs is another 2km away on the other side. If you've hitchhiked across this border, please add information!
Puente Internacional Comandante Andresito on the Ruta Provincial 19. Goes from the Argentinian town Comandante Andresito in Misiones province, to Capanema, State of Paraná. The Argentinian passport control is 800m from the actual border and the Brazilian one 300m. The distance between the two nearest settlements is 38km. Let us know if you hitched this border.
San Antonio Bridge on the Ruta 101 in the town of San Antonio, Misiones province. The Brazilian town is named Santo Antônio do Sudoeste, in State of Paraná. The border crossings are in an urban area a mere 150m apart. Let us know if you hitched this border.
Bernardo de Irigoyen - Barracão on the Ruta 101/14 in the town of Bernardo de Irigoyen, Misiones province. The brazilian town is called Barracão in Paraná State, and there's almost no physical border between the two towns, with multiple crossings. You can get your entrance/exit stamps at the bridge close to the Plaza San Martin on the Argentinian side. Customs offices are within 100m of each other. Let us know if you hitched this border.
Puente Internacional Paraje Rosales on the Ruta 27, the nearest locality being Cruce Caballero, Misiones province. The Brazilian town is called Paraíso, State of Santa Catarina. Argentinian customs is 2km from the actual border and the Brazilian ones 100m. The distance between the two nearest towns is 40km. Let us know if you hitched this border.
El Soberbio Ferry to Porto Soberbo on the Ruta provincial 2, inside the town of El Soberbio, Misiones province. The Brazilian town is Porto Soberbo, State of Rio Grande do Sul, and significantly smaller than its Argentine counterpart. Customs of both countries are directly on the shores of the Rio Uruguay. Let us know if you hitched this border.
Alba Posse Ferry to Porto Mauá on the Ruta provincial 8, in the village of Alba Posse, Misiones province. The Brazilian town is Porto Mauá, State of Rio Grande do Sul. The Brazilian customs is directly on the shore. Let us know if you hitched this border.
Panambí Ferry to Porto Vera Cruz on the Ruta provincial 5, village of Panambí, Misiones province. The Brazilian town is Porto Vera Cruz, State of Rio Grande do Sul. Argentinian customs are on the shore next to the municipal camping. Let us know if you hitched this border.
San Javier Ferry to Porto Xavier on the Ruta provincial 2, town of San Javier, Misiones province. The Brazilian town is Porto Xavier, State of Rio Grande do Sul. Customs of both countries are directly on the shores of the Rio Uruguay. Let us know if you hitched this border.
Garruchos Ferry on the Ruta provincial 37, town of Garruchos, Corrientes province. The Brazilian town is also calles Garruchos, State of Rio Grande do Sul. Location of customs currently unknown - might be a border only for locals - but the ferry definitely exists. Let us know if you crossed here.
Puente Internacional de la Integracion/Ponte Internacional da Integraçao on the Ruta 121 between Santo Tomé, Corrientes province and the Brazilian São Borja, State of Rio Grande do Sul. The Argentinian customs is 3km from the middle of the bridge in the Uruguay river. The location of the Brazilian passport control is unknown, but there's a fair chance the in/out stamps are done in the same building at the Argentinian side (speculation, yes). Enlighten us if you crossed this border.
Alvear - Itaqui ferry on the Ruta Nacional 14 between Alvear and, Corrientes province and the Brazilian Itaqui, State of Rio Grande do Sul. The Argentinian customs is right on the shore and the Brazilian one presumably as well. Please add info if you crossed this border.
Puente Internacional Getúlio Vargas-Agustín Pedro Justo on the Ruta 14 from Paso de los Libres, Corrientes province, to the Brazilian city of Uruguaiana, State of Rio Grande do Sul. This is a big one. Argentinian customs is 1 km before the bridge and Brazilian customs 1 km after. It's doubtful you can walk the 2 km over the bridge. Let us know if you hitched this border.
Uruguay is a super lovely country where hitchhiking and freecamping are fairly easy. Many Argentinians look at Uruguay as a province, not a country, because of its size. All border crossings between Argentina and Uruguay cross a river, either by bridge or by ferry. By all means try to avoid taking Argentinian currency to Uruguay and vice versa as you are going to lose a lot of value when changing (like user Miriam experienced kind of annoyed). If necessary, change to Dollars in between.
Uruguayan border crossing north to south
Puente Internacional Salto Grande roughly on the Ruta Nacional 14 between Concordia, Entre Rios province and Salto in the Salto Department. The bridge is actually 15 km north of both cities, so it's quite the detour. The bridge is also a hydroelectric dam on the Uruguay River and it's one of the biggest border crossings in Uruguay. Argentinian customs is 4 km from the center of the bridge (the actual border) and might do both the Argentinian and the Uruguayan entry/exit stamps. As Concordia and Salto are only separated by 1 km of river, it might be possible to cross from city to city on a foot passenger ferry, but information is scarce. Please add info if you hitched this border.
Puente Internacional General Artigas on a side road of the Ruta Nacional 14 between Colón, Entre Rios province and Paysandú, Paysandú Department. Mind of a Hitchhiker hitched this border from Uruguay to Argentina in 2016 and found out that both the Argentinian and the Uruguayan customs are on the Uruguayan side, about 1 km from the center of the bridge. She didn't get an Uruguayan exit stamp, the reason being "We're both MERCOSUR, we share resources. You can go now". Okay... She got a ride to Colón from a guy who lives there. If you're traveling the other direction, there's an YPF gas station on the Argentinian side that leads to the bridge, about 5 km from the center of the bridge. The distance between the center of Colón and the center of Paysandú is 20 km. There's a bus going from Paysandú center to a neighborhood called Nuevo Paysandú, which is at the road to the border. It's not the busiest border outside the holiday season.
Puente Libertador General San Martín off the Ruta Nacional 14 roughly between Gualeguaychu, Entre Rios province and Fray Bentos, Rio Negro Department. The nearest city of size in Uruguay is Mercedes, Soriano Department. Argentinian customs is 5 km from the center of the bridge. Uruguayan customs is 1.5 km from the center of the brige. The distance between Gualeguaychú and Mercedes is 68 km. User Miriam hitched this border in 2017 to get around expensive ferry rides and went from Buenos Aires to Montevideo in one day. It is forbidden to cross the bridge by foot, so you need a ride across which the border posts were willing to give. You only need one stamp, at the Uruguayan side, because both countries have some kind of treaty. Border police were more than bored and literally painting their nails. Everything tranquilo.
Ferry Cacciola Tigre - Carmelo possibly via Isla Martin Garcia! Tigre is a village next to Buenos Aires capital, inside Buenos Aires province. It's a train ride away and can't really be hitched to from the city. Carmelo is in Carmelo department, Uruguay. The ferry crosses the Rio de la Plata. Info on prices and times have to be Googled by oneself. This is a very interesting way to cross borders. One might get a glimpse or even moor at Isla Martin Garcia.
Isla Martín Garcia is a great mystery. The island is Argentinian territory in Uruguayan waters and has a brother island north of it called Isla Timoteo Dominguez. By now they've grown together and are one, so there's an actual border on these islands. It's a really tiny island with not many people living there. One gets to the island either via Tigre or via the Puerto Madero ferry pier. Google is thy friend. Whether it is possible to go here to Uruguay legally is unknown. The nearest landfall from the island to Uruguay is 4 km and there's a pier over there called "Martin Chico". If you've never done this, it's a great opportunity to give boathitching a try. Let us know if you went to this island and what your next move was!
Ferry Tigre - Colonia del Sacramento. Ticket prices vary. Google before you go. Let us know if you took this ferry to cross the border.
Ferry Buenos Aires - Colonia del Sacramento is by far the most popular way to get to Uruguay. There's three companies that operate on this crossing and there's a ferry leaving every 2 hours. The companies are Buquebus, Seacat Colonia and Colonia express. Seacat is usually the cheapest. You can book your tickets online and if you don't have a credit card, ask an Argentinian CS host to buy it and pay it back to them in cash. Mind of a Hitchhiker took this ferry in 2016 (and 2011) and found out that (somehow) tickets were half price if you paid them in Uruguayan pesos. No guarantee that this is still the case, but it's worth to play around with it. She paid €20 for a one-way ticket. The ferry terminal is in the neighborhood of Puerto Madero in Buenos Aires and can be rather busy on weekends when people do the shopping in Uruguay. In summer, there's more ferries per day and more people taking them. You get the Argentinian exit and Uruguayan entry stamp both on the Argentinian side when you travel in this direction. People are very pushy to go on board. Loads of competition to get a window seat.
Ferry Buenos Aires - Montevideo is a seasonal (summer) ferry that goes directly between the ports of Buenos Aires and the capital of Uruguay: Montevideo. Since the distance to cross is way longer, it might not be financially interesting for a hitchhiker to take. Let us know about pricing if you took this ferry.