The Lander Trail, part of the Congressionally designated California National Historic Trail, served as a shortcut from the main emigrant trails to California and Oregon and to the new gold fields in Montana and Idaho. Emigrants began in towns along the Missouri River and traveled west through Kansas and Nebraska before reaching Wyoming, where about halfway through their five- to six-month journey they could take Lander's Cut-off Road at South Pass after ascending the Continental Divide. From 1841 to 1869, about 350,000 people emigrated west on undeveloped wagon roads in the greatest voluntary mass migration in US history. Responding to public demand for better transportation to the Pacific Coast, Congress passed the Pacific Wagon Road Act in 1857, and in 1858 Frederick Lander supervised construction of a new 256-mile cutoff between South Pass, Wyoming, and Fort Hall, Idaho, one of the first federally funded roads in the West. The route could save emigrants up to seven days of travel while avoiding long desert crossings, and tens of thousands used it from 1859 to 1869. At the New Fork River, one of the most difficult crossings on the Lander Trail, emigrants risked losing supplies, livestock, and even their lives, yet the lush grass and cottonwood trees offered a brief oasis after the Continental Divide, and the good camping and bottleneck at the river crossing made it one of the busiest places on the trail. The completion of the transcontinental railroad twelve years after the 1857 act signaled the end of the emigrant trail era.