Baja California Territory in the context of Territory of Baja California Sur

Alta California (English: Upper California), also known as Nueva California (English: 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 present-day 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.

Ensenada ("inlet") is a city in Ensenada Municipality, Baja California, situated on the Pacific Coast of Mexico. Located on Bahía de Todos Santos, the city had a population of 279,765 in 2018, making it the third-largest city in Baja California. The city is an important international trade center and home to the Port of Ensenada, the second-busiest port in Mexico. Ensenada is a major tourist destination, owing to its warm climate and proximity to the Pacific Ocean, and is commonly known as La Cenicienta del Pacífico ("The Cinderella of the Pacific").

Ensenada was founded in 1882, when the small community of Rancho Ensenada de Santos was made the regional capital for the northern partition of the Baja California Territory. The city grew significantly with the proliferation of mines in the surrounding mountains. While the Mexican Revolution curtailed much of Ensenada's expansion, the onset of Prohibition in the United States transformed the city into a popular tourist destination for Americans seeking entertainment and alcohol. Ensenada's reputation as a resort town was cemented by the 1950s and 1960s, which saw a construction boom and the city's rise in international prominence outside of North America.