Texas was originally part of Mexico, achieving independence as the Republic of Texas in 1836. The United States acquired the area of Texas through annexation and Texas was admitted to the Union on March 1, 1845, as the 28th state. At the time of statehood, Texas included part of present-day Colorado, Kansas, New Mexico, Oklahoma, and Wyoming. Texas sold territory to the United States in 1850 to assume generally the same boundary as the present state, but there were some subsequent revisions. In 1896, the Supreme Court ruled the Texas claim to the Greer County area in southwest Oklahoma to be invalid, and the area was officially deemed to be part of Oklahoma. An additional boundary dispute with Oklahoma was settled in 1930 by adding a narrow strip of territory to Texas. As the Rio Grande has changed its course, the United States and the Republic of Mexico have made periodic adjustments to their boundary that affected the boundary of Texas.