National Colorado Day Date in the current year: August 1, 2025

Colorado is one of the so-called Mountain States, located in the Mountain West subregion of the United States. It is bordered by Wyoming, Nebraska, Kansas, Oklahoma, New Mexico, Utah, and Arizona. The official nickname of Colorado is the “Centennial State” because it was admitted to the Union exactly a century after American independence.

The territory of what is now Colorado has been inhabited by Native American tribes for over 13,000 years. They included the Ancestral Puebloans, the Ute, the Apache, the Comanche, the Arapaho, and the Cheyenne.

The first Europeans to set foot in the region were Spanish conquistadors, for example, Juan de Oñate, the founder of the province of Santa Fé de Nuevo México (present-day New Mexico). In 1706, Juan de Ulibarri claimed the region for Spain. The first European settlement in Colorado was established by Juan Bautista de Anza in 1787, but it was very short-lived. It was the only attempt of the Spanish to found a settlement north of the Arkansas River.

In 1803, the United States claimed the eastern flank of the Rocky Mountains in accordance with the terms of the Louisiana Purchase, but Spain laid a claim of sovereignty over the territory as well. In 1806, the United States Army organized a reconnaissance expedition led by Zebulon Pike into the disputed region. Spanish cavalry arrested Pike and his men in the San Luis Valley several months later.

The United States officially relinquished its claim in 1819 by signing the Adams-Onis Treaty with Spain. In 1821, Mexico won its war of independence, and the Spanish the province of Santa Fé de Nuevo México, which included the territory of what is now Colorado, became Mexican.

In 1848, Mexico lost the Mexican-American War and had to relinquish its northern territories by the Treaty of Guadalupe Hidalgo, opening the Southern Rocky Mountains to American settlers. Most settlers, however, avoided the mountainous region for the next decade. The situation changed in 1858, when small amounts of gold were found in various streams in the South Platte River Valley, resulting in the Pike’s Peak Gold Rush. Over the next few years, approximately 100,000 gold seekers arrived in the region.

In 1859, there was an attempt to establish the Territory of Jefferson, but it failed to secure legal recognition by the federal government. As a compromise, the Territory of Colorado was created in 1861. In March 1875, the Congress passed an enabling act, allowing Colorado to become a state provided that it met the requirements. On August 1, 1876, Colorado was admitted to the Union as the 38th state.

Although Colorado Day isn’t a state holiday, it is marked by various events and activities held in the Colorado State Capitol, such as speeches, concerts, live historical presentations, exhibitions, games and activities for the whole family, trivia quizzes, etc.

An alternative celebration of Colorado called National Colorado Day is held on April 12. It was created in 2017 by National Day Calendar as part of its National State Days project, which celebrates the states one at a time in the order of their admission to the Union.