implementation of the Danish constitution. North America Danish West Indies (1666–1917) Denmark–Norway acquired the island of St. Thomas in 1671 and St. Jan (now St. John) in 1718, and bought St. Croix from France in 1733. All of the islands' economies were based primarily on sugar. These islands were known as the Danish West Indies and were eventually sold to the United States in 1917 for 25 million dollars. Several Danish-American succession talks had been made since 1870 due to a rising number of riots and unrest from the poorer English-speaking population. The Zahle Government (1914-1920) held a heavily boycotted election for Danish mainland constituencies, which produced a minority for the sale of the islands. The United States hoped to use them as naval bases. Since 1917, the islands have been known as the United States Virgin Islands. Greenland (1814–present) Greenland was settled by immigrants from Iceland and Norway in the Viking Age after the arrival of Erik the Red in 995 or 996. Medieval Greenland was a bishopric with 22 churches and 2 convents under the archdiocese of Nidaros. In 1261, the Greenlanders became subjects of the Kingdom of Norway (872–1397). With the ratification of the Kalmar Union in 1397, Denmark–Norway inherited Greenland. After the Norse settlement in Greenland finally disappeared in the 15th century, Europeans did not settle the island again until 1721, when the Lutheran minister Hans Egede arrived and established the town now known as Nuuk. After Norway was ceded to the king of Sweden in 1814 following the Napoleonic Wars, Denmark retained the old territorial claims as a condition of the Treaty of Kiel. The development and settlement of Greenland accelerated in 1945, instigated by the region's geostrategic importance in the Cold War era, itself exemplified and manifested by the U.S. Air Base of Thule from 1943. Another reason and driving force was the emergence of fundamental technical abilities, such as aircraft and icebreakers at Greenland's disposition, giving the otherwise remote island a supply situation somewhat similar to Europe. Following a period of increasing integration in the 19th century, Greenland was incorporated into Denmark in 1953 with the implementation of the Danish constitution. Legacy Greenland and the Faroe Islands were the last vestiges of the colonial empire. Greenland's colonial status ceased in 1953, becoming an integral part of the Kingdom of Denmark. It gained home rule in 1979 and further autonomy, including self-determination, in 2009.