The Line of Demarcation was a line drawn along a meridian in the Atlantic Ocean as part of the Treaty of Tordesillas in 1494 to divide new lands claimed by Portugal from those of Spain. This line was drawn in 1493 after Christopher Columbus returned from his maiden voyage to the Americas. The Mason-Dixon line (or "Mason and Dixon's Line") is a demarcation line between four U.S. states, forming part of the borders of Pennsylvania, Maryland, Delaware, and West Virginia (then part of Virginia).