 Independence had been the trailhead for several key emigrant trails, prior to 1846 notably both the Santa Fe Trail and one alternative eastern starting branch of the Oregon Trail.After the Mexican–American War treaty of 1848, the Oregon Trail's trailhead became a trailhead of the California Trail and an alternative beginning for the Mormon Trail.In 1850, the United States Congress passed the Swamp Land Act providing land grants to build stronger levees.