As many as half a million people crossed what’s now Wyoming in the mid-19th century before the transcontinental railroad was built. Their trails followed the North Platte and Sweetwater rivers west to South Pass, after which they divided into various routes bound for Oregon, Utah or California. They were making the journey of a lifetime, on routes blazed by Indians and trappers, and then worn deep and wide by thousands of wagons and perhaps millions of draft animals. These trails remain largely unchanged in Wyoming. Their white-topped wagons still hold an important place in the national imagination.