Although Interstate 80 begins at U.S. 101 in San Francisco, original plans called for the Interstate to continue west through Golden Gate Park to the Pacific Ocean near the famous Ocean Beach area. This plan was halted due to community opposition. As a result, Interstate 80 is a few miles shorter than originally planned. Since the Central Freeway viaduct was mostly torn down, Interstate 80 now ends at the series of U.S. 101 exits near Van Ness Avenue. This terminus is somewhat in dispute; some say that Interstate 80 actually ends at the Embarcadero exit.
Interstate 80 largely replaced its companion U.S. routes in the West and parallels them in the East. Between San Francisco and Park City, Interstate 80 replaced U.S. 40. Sections of original U.S. 40 are still in use as local county roads in California, while many segments of U.S. 40 in Nevada were directly replaced by Interstate 80. Today, U.S. 40 begins its easterly journey at its interchange with Interstate 80 in Park City. Between Park City and Echo Junction, Interstate 80 replaced U.S. 189 (and U.S. 530 before it). At Echo Junction, Interstate 80 met its companion for most of its country-country trek: U.S. 30.
U.S. 30 is the Lincoln Highway through Wyoming, Nebraska, Iowa, Illinois, Indiana, and Ohio. It closely parallels Interstate 80 in Wyoming and Nebraska, combining with the freeway in the least populated areas (such as the continuously merged portion of Interstate 80 and U.S. 30 between Granger and Walcott in Wyoming, a distance of 170 miles). At Grand Island, Nebraska, U.S. 30 stays north of Lincoln and Omaha; Interstate 80 instead follows U.S. 34 between Grand Island and Lincoln and U.S. 6 from Lincoln to the Quad Cities via Omaha and Des Moines. U.S. 6 merges with Interstate 80 several times through Iowa, and it closely parallels Interstate 80 through Illinois before joining the freeway again in Lansing.
Meanwhile, Interstate 80 does not intersect U.S. 30 until Joliet. Having avoided Des Moines and the Quad Cities, U.S. 30 heads southeast to avoid downtown Chicago. U.S. 30 continues on this trajectory en route to Fort Wayne, Pittsburgh, and Philadelphia; it does not intersect Interstate 80 again. Interstate 80 instead remains close to U.S. 6 and U.S. 20 as they skirt the southern edge of the Great Lakes. Interstate 80 is tolled through Indiana and Ohio, so the parallel U.S. 6 and U.S. 20 provide free alternate routes.
Bypassing Cleveland to the south, Interstate 80 leaves both U.S. 6 and U.S. 20, as they follow Interstate 90. For the first time, Interstate 80 follows a path that was not previously tread by a U.S. route (it followed the Keystone Shortway). Leaving the Ohio Turnpike at North Jackson, Interstate 80 briefly parallels U.S. 62 through Sharon, then again finds itself without a companion U.S. route. This situation persists for the most part across Pennsylvania, with the exception of U.S. 322 from Clarion to State College and a brief merge with U.S. 220 near State College. Finally entering New Jersey, Interstate 80 picks up U.S. 46, a route which is almost entirely located within New Jersey -- in fact, it never went any farther west than Pennsylvania 611 (former U.S. 611). U.S. 46 follows Interstate 80 all the way to its end in Ridgefield Park; in fact, U.S. 46 officially continues all the way to the midpoint of the George Washington Bridge where Interstate 95 leaves New Jersey and enters New York.