A political demarcation line is a geopolitical border, often agreed upon as part of an armistice or ceasefire. Moroccan Wall, delimiting the Moroccan-controlled part of Western Sahara from the Sahrawi-controlled part The Line of Demarcation was one specific 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). It was surveyed between 1763 and 1767 by Charles Mason and Jeremiah Dixon in the resolution of a border dispute between British colonies in Colonial America. The Blue Line is a border demarcation between Lebanon and Israel published by the United Nations on 7 June 2001 for the purposes of determining whether Israel had fully withdrawn from Lebanon. The term Green Line is used to refer to the 1949 Armistice lines established between Israel and its neighbours (Egypt, Jordan, Lebanon and Syria) after the 1948 Arab–Israeli War. The Purple Line was the ceasefire line between Israel and Syria after the 1967 Six-Day War. The Green Line (Lebanon) refers a line of demarcation in Beirut, Lebanon during the Lebanese Civil War from 1975 to 1990. It separated the mainly Muslim factions in West Beirut from the predominantly Christian East Beirut controlled by the Lebanese Front. The McMahon Line is a line dividing China and India, drawn on a map attached to the Simla Convention, a treaty negotiated between the British Empire, China, and Tibet in 1914. The Military Demarcation Line, sometimes referred to as the Armistice Line, is the border between North Korea and South Korea. The Military Demarcation Line was established by the Korean Armistice Agreement as the line between the two Koreas at the end of Korean War in 1953.