History of California before 1900

Human history in California begins with indigenous Americans first arriving in California some 13,000–15,000 years ago. Exploration and settlement by Europeans along the coasts and in the inland valleys began in the 16th century. California was acquired by the United States under the terms of the 1848 Treaty of Guadalupe Hidalgo following the defeat of Mexico in the Mexican–American War. American westward expansion intensified with the California Gold Rush, beginning in 1849. California joined the Union as a free state in 1850, due to the Compromise of 1850. By the end of the 19th century, California was still largely rural and agricultural, but had a population of about 1.4 million.

The most commonly accepted model of migration to the New World is that peoples from Asia crossed the Bering land bridge to the Americas some 16,500 years ago. The remains of Arlington Springs Man on Santa Rosa Island are among the traces of a very early habitation, dated to the Wisconsin glaciation (the most recent ice age) about 13,000 years ago. In all, some 30 tribes or culture groups lived in what is now California, gathered into perhaps six different language family groups. These groups included the early-arriving Hokan family (winding up in the mountainous far north and Colorado River basin in the south) and the recently arrived Uto-Aztecan of the desert southeast. This cultural diversity was among the densest in North America, and was likely the result of a series of migrations and invasions during the last 10,000–15,000 years. At the time of the first European contact, Native American tribes included the Chumash, Maidu, Miwok, Modoc, Mohave, Ohlone, Pomo, Serrano, Shasta, Tataviam, Tongva, Wintu and Yurok.