The Californias followed by Baja California
The Californias (Spanish: Las Californias), occasionally known as The Three Californias or Two Californias, are a region of North America spanning the United States and Mexico, consisting of the U.S. state of California and the Mexican states of Baja California and Baja California Sur. Historically, the term Californias was used to define the vast northwestern region of Spanish America, as the Province of the Californias (Spanish: Provincia de las Californias), and later as a collective term for Alta California and the Baja California Peninsula.Originally a single, vast entity within the Spanish Empire, as the Californias became defined in their geographical limits, their administration was split various times into Baja California (Lower California) and Alta California (Upper California), especially during the Mexican control of the region, following the Mexican War of Independence. As a part of the Mexican–American War (1846–48), the American Conquest of Alta California saw the vast Alta California territory ceded from Mexico to the United States. The populated coastal region of the territory was admitted into the Union in 1850 as the State of California, while the vast, sparsely populated interior region would only later gain statehood as Nevada, Utah, and parts of Arizona, Wyoming, and Colorado.
Today, Californias is a collective term to refer to the American and Mexican states bearing the name California, which share geography, history, cultures, and strong economic ties.