Alta California

Alta California ('Upper California'), also known as Nueva California ('New California') among other names, was a province of New Spain formally established in 1804. Along with the Baja California peninsula, it had previously comprised the province of Las Californias, but was made a separate province in 1804 (named Nueva California). Following the Mexican War of Independence, it became a territory of Mexico in April 1822 and was renamed Alta California in 1824.

The territory included all of the U.S. states of California, Nevada, and Utah, and parts of Arizona, Wyoming, and Colorado. The territory was re-combined with Baja California (as a single departamento) in Mexico's 1836 Siete Leyes (Seven Laws) constitutional reform, granting it more autonomy. That change was undone in 1846, but rendered moot by the outcome of the Mexican–American War in 1848, when most of the areas formerly comprising Alta California were ceded to the U.S. in the treaty which ended the war. In 1850, California joined the union as the 31st state.

The El Camino Real trail established by the Spanish extended from Mexico City west to Santa Fe, and California, as well as east to Florida. To the southeast, beyond the deserts and the Colorado River, lay the Spanish settlements in Arizona. Spanish soldiers, settlers, and missionaries invaded the homelands of the Indigenous peoples of California, people of the Great Basin, and the Pueblo peoples in the establishment of Alta California.

Evidence of Alta California remains in the numerous Spanish place names of American cities such as San Diego, Santa Ana, Los Angeles, San Jose, San Francisco, and San Bernardino.