In 2026 Colorado and the United States will celebrate our Sesquisemiquincentennial. That is a word for the combination of the 250th Anniversary of the Declaration of Independence, the nation’s semiquincentennial, and Colorado’s 150th anniversary, sesquicentennial, of statehood.
You will start seeing the symbol around a lot.
Colorado, the 38th state in the union, is the only state to observe the dual anniversaries. To begin, let’s give Colorado statehood and the San Luis Valley some perspective in time.
Paleoindian cultures were present in the San Luis Valley about 11,000 years ago. Colorado was inhabited by the Utes, ancestral Puebloan, Arapaho Cheyenne, Apache, Comanche, Pawnee and Shoshone and Navajo tribes before European exploration. The San Luis Valley was the ancestral home to the Utes. Mesa Verde was inhabited around 1200 AD. The Mexico City area has been inhabited by people since 100 AD; it was an Aztecan city around the year 1325, and was settled by Spaniards in 1521. Santa Fe, originally inhabited by the Tanoan people, was developed in 1598 by Don Juan de Onate as a province of New Spain. Jamestown was established in 1607. St. Louis, originally the center of Native Mississippian culture, was founded in 1764.
The expansion of Spanish exploration moved into where San Francisco is today in 1776, five days before the signing of the Declaration of Independence. Delaware was the first state to join the Union in 1787. The Louisiana Purchase was in 1803.
Zebulon Pike overwintered in the San Luis Valley on the Conejos River in 1806-07. The Santa Fe Trail was established in 1821 but did not officially travel through the Valley. In the heyday of the Old Spanish Trail, during the 1830s, the northern branch extended from Santa Fe, Taos, through the San Luis Valley over Cochetopa Pass and on to present-day Montrose and Los Angeles. Bents Fort began operating in 1833 along the Arkansas River. Pueblo became a trading post in 1842. The San Luis Valley and New Mexico became a part of the United States in 1848 through the Treaty of Guadalupe Hidalgo. Provisions of the treaty included the protection of property and civil rights of Mexican nationals living within the new boundaries. Guadalupe settlers arrived from Taos in 1848, and later moved to the Conejos townsite location, which was established in 1854. La Plaza de los Manzanares, originally settled as a defense measure in 1849, became the town of Garcia in 1915.
San Luis was settled by Spanish families arriving from New Mexico in 1851.
Fort Massachusetts was built in 1852 at the base of Blanca Peak and then relocated to Fort Garland in 1858.
The Colorado Gold Rush began in 1858 and Denver was established that same year. Sequentially, first, in the summer of 1848 placer gold was discovered in a creek bed in present-day Englewood. Then, the town of Auraria with 50 cabins and a post office, became the center of activity in October. General William Larimer preferred a different location close by and established the town of Larimer which was renamed Denver City to seek the favor of Kansas Territorial Gov. James. W. Denver.
Del Norte was plotted in 1871. Saguache, founded by Otto Mears, became a townsite in 1874. The Saguache Chronicle Newspaper was first published in 1876. Colorado became a state in 1876. Leadville was founded in 1877 by Horace Tabor and August Meyer. Buena Vista soon followed in 1879. San Luis incorporated in 1885.
Alamosa was incorporated in August 1878 as the temporary terminus of the Rio Grande railroad. Monte Vista, originally named Henry, in 1884 was developed close to canal systems and rail lines. It was renamed Monte Vista in 1886.
The Jan. 1, 2026, edition of the New York Times mentioned ways to be “good and proactive” in the new year. One unidentified reader answered that “Living in the same place for 30 years is a great adventure when one pays attention.” In the following months more details about the history of the San Luis Valley will be brought to your attention.
Numerous resources were used to keep these historical dates as correct as possible: History Colorado, Sangre de Cristo National Heritage Area, US Parks Service, Visit
Alamosa, Chicano and Latino History Project, and Wikipedia.
Read more about the history of the Valley in these archived articles from the San Juan Prospector: Historical Story of Agriculture In the Sunny San Luis Valley, published Jan. 1. 1926. And Del Norte 50 Years Ago, published in the same edition.
