Christopher Columbus discovered South America in 1498. At the time of his discovery, he and his crew thought they had landed on an island. He named the island Isla Santa.
Christopher Columbus was a businessman who was looking for a western sea route to China, India and Asia. Despite having an understanding of the world, Columbus, like many explorers, did not realize the world was so large and did not understand that South America was a continent.
When Columbus landed in Cuba, he thought he was in China and when his ship made its way to Hispaniola, he thought he had discovered Japan.