The first Europeans to claim dominion over California were the Spanish, who slowly established mission towns and ranches. After the Mexican Revolution against Spanish rule, California fell under the rule of Mexico in 1821 but continued to be ignored due to constant internal strife within the Mexican government. The United States was expanding ever westward in the 19th century, and in June 1846, the Mexican-American War began. When American settlers of Sonoma, California heard about the fighting, they began a revolt. The war ended in 1847 and established the U.S.-Mexico border at its current boundaries.