[172] After meeting with Gillespie, Army captain John C. Frémont led settlers in northern California to overthrow the Mexican garrison in Sonoma in what became known as the Bear Flag Revolt.[173] In August 1846, American forces under Kearny captured Santa Fe, capital of the province of New Mexico, without firing a shot.[174] Almost simultaneously, Commodore Robert F. Stockton landed in Los Angeles and proclaimed the capture of California.[175] After American forces put down a revolt, the United States held effective control of New Mexico and California.[176] Nevertheless, the Western theater of the war would prove to be a political headache for Polk, since a dispute between Frémont and Kearny led to a break between Polk and the powerful Missouri senator (and father-in-law of Frémont), Thomas Hart Benton.[177]

War News from Mexico, 1848 painting by Richard Caton Woodville
The initial public euphoria over the victories at the start of the war slowly dissipated.[178] In August 1846, Polk asked Congress to appropriate $2 million as a down payment for the potential purchase of Mexican lands. 