Explorer Amerigo Vespucci was born on March 9, 1454. Vespucci moved to Seville, Spain, in 1492 and in 1499 conducted an exploratory expedition of the mouth of the Amazon River in what is now Brazil. Upon his return to Spain in 1500, he went into service for Portugal, returning to South America to explore that continent’s coastline. Vespucci would later devise a method for determining the Earth’s circumference at the equator; the number he arrived at was close to the actual circumference. This number, which was much larger than previous estimates, led him to believe that South America was a separate continent from Asia, contrary to common belief. The American continents are named for Vespucci.