Longitude is a geographic coordinate that specifies the east–west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Meridians are imaginary semicircular lines running from pole to pole that connect points with the same longitude. The prime meridian defines 0° longitude; by convention the International Reference Meridian for the Earth passes near the Royal Observatory in Greenwich, south-east London on the island of Great Britain. Positive longitudes are east of the prime meridian, and negative ones are west.

Christopher Columbus was an Italian explorer and navigator from the Republic of Genoa who completed four Spanish-based voyages across the Atlantic Ocean sponsored by the Catholic Monarchs, opening the way for the widespread European exploration and European colonization of the Americas. His expeditions were the first known European contact with the Caribbean and Central and South America.