The highway roughly traces other historically significant travel routes in the Western United States : the Oregon Trail across Wyoming and Nebraska , the California Trail across most of Nevada and California , the first transcontinental airmail route , and except in the Great Salt Lake area , the entire route of the First Transcontinental Railroad .
The highway roughly traces other historically significant travel routes in the Western United States : the Oregon Trail across Wyoming and Nebraska , the California Trail across most of Nevada and California , and except in the Great Salt Lake area , the entire route of the First Transcontinental Railroad .