The Treaty of Tordesillas divided overseas spheres between Spain and Portugal in 1494.
Signed on 7 June 1494, the treaty moved the boundary established by an earlier papal arrangement. It placed a north–south line roughly 370 leagues west of the Cape Verde Islands; lands east of the line were assigned to Portugal and lands west to Castile, the kingdom that formed the Spanish monarchy with Aragon.
The agreement was designed to reduce conflict after Christopher Columbus’s 1492 voyage and competing claims in the Atlantic. Its geographical line was difficult to determine precisely because longitude could not yet be measured accurately at sea.
The treaty helped explain Portugal’s claim to Brazil after Pedro Álvares Cabral’s 1500 expedition, although the coast’s exact position relative to the line was debated. Spain and Portugal later negotiated the Treaty of Zaragoza in 1529 over their competing claims in Asia.