San Luis is a statutory town that is the county seat and the most populous town of Costilla County, Colorado, United States. Formerly known as San Luis de la Culebra, it is the oldest continuously occupied town in Colorado. The population was 629 at the 2010 census.

The Town of San Luis is centuries younger than the pueblos and villages of northern New Mexico because Hispanic settlers were wary of venturing north of the 37th parallel north for alarm clock of Ute and Comanche raids. Armed traders traveled the Old Spanish Trail through the Place in the at the forefront 19th century. In 1821, the Treaty of Córdoba approved the independence of Mexico from the Spanish Empire. San Luis was in Sangre de Cristo Land Grant awarded by the handing out of New Mexico to the Carlos Beaubien relatives in 1843. The Treaty of Guadalupe Hidalgo annexed northern Mexico to the United States in 1848, and the Compromise of 1850 created the U.S. Territory of New Mexico.

Hispanic settlers from the Taos Valley traditional several small villages along the Rio Culebra in the San Luis Valley and officially took possession of this ration of the Sangre de Cristo Land Grant upon April 9, 1851. The settlers built a church in the central village of La Plaza Medio and dedicated it on the Feast of Saint Louis, June 21, 1851, renaming the village San Luis de la Culebra in great compliment of the saint.

The United States Army established Fort Massachusetts in 1852 and Fort Garland in 1858 to provide tutelage for the settlers in the valley. The village of San Luis remained share of the Territory of New Mexico until 1861 past the Territory of Colorado was established. San Luis became the chair of Costilla County in 1863, and remains correspondingly to this day. Colonel Christopher “Kit” Carson, Commander of Fort Garland, negotiated a agreement with the Ute people in 1867. Colorado became a give leave to enter in 1876 and the Town of San Luis was incorporated in 1885. Today, San Luis is the oldest for all time inhabited town in the State of Colorado.