The territory of Alta California, which includes modern-day California, was settled by the Viceroyalty of New Spain from 1683 onwards. It became part of an independent Mexico in 1821. John Sutter, a German-Swiss settler, arrived in the region in 1839. He established a colony at New Helvetia (now part of Sacramento), in the Central Valley. The United States conquered the region during the Mexican-American War (1846–1848): California was overrun by US forces in 1846 and a ceasefire in the region was agreed in January 1847. A peace treaty for the wider war had not yet been completed when Sutter decided to begin construction of a sawmill in the forest about 30 miles north-east of his existing colony. Sutter employed James Wilson Marshall, a carpenter originally from New Jersey, to supervise construction of the new building.