The earliest evidence I can think of is the Waldseemueller map from 1507, which was the first point in time when America (which he and a colleague coined) shows up on the map as a distinct place. North America wasn't know to be connected yet, though.

Wally's map is based on Vespucci's publication, Novus Mundus (sp? On my phone). That obviously predates the map but not by terribly long.