A border drawn on a median strip
The Brazil-Uruguay border stretches for 1,069 kilometers, but its most peculiar section is in the twin towns of Chuí (Brazil) and Chuy (Uruguay). Here, the international boundary is not a river or a fence, but the central median of a single street known as Avenida Internacional. This thoroughfare has a dual identity; on the Brazilian side, it is named Avenida Uruguai, while on the Uruguayan side, it is called Avenida Brasil. Pedestrians can cross from one country to another simply by stepping over the curb, creating one of the most accessible international borders in the world.
The final section of the border is defined by the Chuí Stream, or Arroio Chuí, a 45-kilometer-long waterway that originates in the coastal plains of Brazil and flows into the Atlantic Ocean. The stream itself is physically unremarkable, but it holds national significance in Brazil. The expression "do Oiapoque ao Chuí" (from the Oiapoque to the Chuí) refers to the entirety of the nation, referencing the rivers that mark the northern and southern ends of the Brazilian coast. The exact southernmost point of Brazil is located on a bend in this stream, a short distance from its mouth.
The history of this border is complex, from colonial disputes between Spain and Portugal. A series of treaties, including the Treaty of Madrid (1750) and the First Treaty of San Ildefonso (1777), attempted to establish clear boundaries. The current border was largely finalized with a treaty in 1851, which established the Chuí stream as the southern limit. The town of Chuí in Brazil was officially established as a municipality in 1997.
An economy of porousness
The open nature of the Chuí border has created a unique local economy. The Uruguayan side, Chuy, is famous for its duty-free shops, or "free shops," which attract shoppers from Brazil looking for lower prices on imported goods like electronics, cosmetics, and beverages. Transactions are commonly conducted in Brazilian Reais, Uruguayan Pesos, and U.S. Dollars, often within the same store.
This economic disparity and the ease of crossing contribute to a thriving informal economy, including widespread smuggling. The flow of goods across this boundary is a part of daily life. The languages are equally fluid. While Portuguese and Spanish are the official languages, daily interaction has produced a hybrid dialect known as "Portuñol," a mix of both languages that facilitates cross-border communication.
The urban area is a conurbation, a single city that happens to be bisected by an international line. Residents move freely between the two sides for work, shopping, and family visits, often ignoring the formalities of a typical border crossing. This creates a distinct social environment where national identities are blended and the international border seems abstract. This dynamic is not unique to Chuí; the cities of Santana do Livramento (Brazil) and Rivera (Uruguay) share a similar open-border relationship.