Treaty of Tordesillas
The Treaty of Tordesillas (June 7, 1494) was an agreement which divided the non-Christian world into two zones of influence, one for Spain and the other for Portugal. The line was drawn 100 leagues west of the Cape Verde Islands. Spain gained west of the line while Portugal was given possession of any unclaimed territory to the east of the line.
The treaty originated in 1493, when Pope Alexander VI attempted to settle a dispute between Spain and Portugal by giving the New World to Spain while rewarding Portugal with claims to India and Africa. The Treaty of Tordesillas formalized this agreement with a key change that shifted the demarcation line to a circle, which enabled Portugal to claim Brazil also.