According to signage, I-80 begins at its intersection with U.S. Route 101 in San Francisco. However, the San Francisco Skyway is not part of the Interstate Highway System; the Interstate actually begins at the west end of the Bay Bridge, at the ramps formerly connecting to the Embarcadero Freeway. Thus the first 1.20 miles (1.93 km) of the signed Interstate are not an actual Interstate.
When I-80 was first approved, it was to head north on the Central Freeway (US 101) and west on the never-built Panhandle Freeway, ending at planned I-280 (State Route 1) in Golden Gate Park. A January 1968 amendment moved I-280 to its present alignment, removed Interstate 480, and truncated I-80 to the Embarcadero Freeway (then I-280, formerly I-480). These changes were made on the state level later that year, but Route 80 was only truncated to US 101. (The Central Freeway remained part of US 101, and the Panhandle Freeway became State Route 241. The Panhandle Freeway was later cancelled in the wake of the Freeway Revolts, and the State Route 241 designation has since been reassigned to an unrelated stretch of highway in Orange County) The San Francisco Skyway, which had already been signed as part of I-80, has remained a de facto section of Interstate 80 to the present day and remains listed as part of Route 80 in California.
Sierra Nevada portion
Crossing the Sierra Nevada, I-80 regularly gets snow at higher elevations from fall to spring. The California Department of Transportation (Caltrans) sometimes requires vehicles to use snow tires, snow chains or other traction devices in the mountains during and after snowstorms. Checkpoints are often utilized to enforce chain restrictions prior to entering the Sierra Nevada.
I-80 crosses the Sierra Nevada crest at the Donner Summit in Nevada County at the elevation 2,206 metres (7,240 ft) westbound and 2,203 metres (7,230 ft) eastbound. The pass is generally open year around, is plowed in winter, but may be temporarily closed during the worst snowstorms. Donner Pass is just a couple miles to the south.
In the state of Nevada, Interstate 80 runs northeast from the Lake Tahoe region near Reno to Battle Mountain. At Battle Mountain, it turns east to the salt flats of Utah via Elko. In Nevada, I-80 is routed along the Truckee and Humboldt rivers.
The stretch of I-80 through Nevada is largely desolate and mountainous. Services are limited compared to I-80 in other states.
After crossing Utah's western border, I-80 crosses the desolate Bonneville Salt Flats west of the Great Salt Lake. The longest stretch between exits on an Interstate Highway is located between Wendover and Knolls, with 37 miles (60 km) between those exits. This portion of I-80, crossing the Great Salt Desert, is extremely flat and straight, dotted with large warning signs about driver fatigue and drowsiness.
East of the salt flats, I-80 passes through Salt Lake City, where it merges with I-15 for three miles before entering the Wasatch Mountains east of the city. It ascends Parley's Canyon and passes within a few miles of Park City as it follows a route through the mountains towards Wyoming.
The route of the Utah section of I-80 is defined at Utah Code Annotated ¡ì 72-4-113(10).
In the state of Wyoming, I-80 reaches its maximum elevation of 8,640 feet (2,633 m) above sea level between Cheyenne and Laramie, Wyoming. Farther west in Wyoming, the interstate passes through the Red Desert and over the Continental Divide. The roadway actually crosses the divide twice, as two ridges of the Rocky Mountains form the Great Divide Basin where water cannot escape.
I-80 enters Nebraska west of Bushnell. The western portion of I-80 in Nebraska runs very close to the state of Colorado, without entering the state; the intersection of Interstate 76 and I-80 is visible from the Colorado-Nebraska state line. From its intersection with I-76 to Grand Island, I-80 lies in the valley of the South Platte and Platte Rivers. The longest straight stretch of interstate anywhere in the system is the approximately 72 miles of I-80 occurring between Exit 318 in the Grand Island area and milemarker 390 near Lincoln. Along this length the road does not vary from an ideally straight line by more than a few yards. After Lincoln, I-80 turns northeast towards Omaha. It then crosses the Missouri River in Omaha to go into Iowa.
Part of Interstate 80 in Nebraska is marked as a Blue Star Memorial Highway.
In the state of Iowa, Interstate 80 runs from the I-80 bridge over the Missouri River east to the Quad Cities and the Fred Schwengel Memorial Bridge over the Mississippi River. It is the main east-west arterial freeway through south-central Iowa, and the main east-west Interstate in the state.
In Iowa I-80 serves the cities of Council Bluffs, Des Moines, Iowa City, and the Iowa portion of the Quad Cities - including Davenport and Bettendorf.
Interstate 80 holds a special place in the hearts of those at Drake University in Des Moines, Iowa. In 1999, Andrew Classen (Associate Professor of Trumpet and Director of Jazz Studies) composed the big band chart,"I-80 Shuffle", commemorating the great highway that passes through the university's hometown. The tune can be heard on the album Rush Hour by Classen's award-winning band, the Drake University Jazz Ensemble I . "I-80 Shuffle" is currently in print and published by C. L. Barnhouse Company in Oskaloosa, Iowa.
In the state of Illinois, I-80 runs from the Fred Schwengel Memorial Bridge across the Mississippi River south to an intersection with I-74. It then runs due east across north-central Illinois just north of the Illinois River to Joliet. I-80 continues east and joins I-94 just before entering the state of Indiana.
The portion of I-80 that runs concurrent with Interstate 294 is a part of the Tri-State Tollway.
In the state of Indiana, I-80 runs concurrent with another Interstate highway for its entire length. It runs with I-94 on the Borman Expressway before joining I-90 to Ohio on the Indiana Toll Road.
The portion of I-80 between La Porte, Indiana and Toledo, Ohio runs (with I-90) within ten miles (16 km) of the Michigan state line. From the State Route 9 and I-80 intersection, the sign marking the Indiana-Michigan state line is visible. At another point in northern Indiana, I-80 comes within about 200 yards (meters) from the Michigan border.
In the state of Ohio, I-80 enters with I-90 from the Indiana Toll Road and immediately becomes the "James W. Shocknessy Ohio Turnpike", more commonly referred to as simply the Ohio Turnpike. The two Interstates cross rural northwest Ohio and run just south of the metropolitan area of Toledo. In Rossford, Ohio it intersects with Interstate 75 in an area known as the Crossroads of America. This intersection is one of the largest intersections of two interstate highways in the United States.
In Lorain, just west of Cleveland, I-90 splits from I-80 and runs northeast as a freeway. I-80 runs east-southeast through the southern suburbs of Cleveland and retains the Ohio Turnpike designation. Just northwest of Youngstown, the Ohio Turnpike continues southeast onto Interstate 76, while I-80 runs east to the north of Youngstown, entering Pennsylvania south of Sharon, Pennsylvania.
In the state of Pennsylvania, I-80 is the main east-west Interstate-standard highway through central Pennsylvania. It runs from the Ohio state line near Sharon to the Delaware Water Gap Toll Bridge over the Delaware River,and is called the Confair Memorial Highway.
I-80 serves no major metropolitan areas in Pennsylvania directly. Spurs from I-80 run to State College, Williamsport, Scranton and Wilkes-Barre. I-80 intersects I-79 in Western Pennsylvania which connects with Erie (about 75 miles to the north) and Pittsburgh (about 55 miles to the south). Interstate 80's highest point (east of the Mississippi) is also located in Pennsylvania, near Exit 111 near Penfield, in Clearfield County.
In 2007, the Pennsylvania Turnpike Commission, combined with state legislature Act No. 44, initiated plans to enact a tolling system on the entire span of Interstate 80 throughout the Commonwealth of Pennsylvania. On October 15, 2007, PennDOT and the Pennsylvania Turnpike Commission signed a 50-year lease agreement, which will allow the Commission to maintain and, eventually, toll I-80.
The portion of 80 that goes through New Jersey is sometimes called the Bergen-Passaic Expressway. I-80 does not go all the way to New York City via the George Washington Bridge. Its designated end is about four miles (6 km) short of New York City in Teaneck, New Jersey. There, it joins and becomes designated as I-95, which does cross the bridge. This has led to some confusion because this I-95 segment is also signed with "TO I-80" signs heading southbound from the George Washington Bridge, and many maps show this section as I-80/95. The tolled section of the New Jersey Turnpike ends at exit 18, which is actually just the toll plaza at the northern terminus. The next exit on I-95 is exit 68, which is consistent with the exit numbering on I-80, which are 68A and 68B, respectively. (The truth is that the exit numbers on this section of I-95 match the mile markers on I-95 had the Somerset Freeway been built. The fact that they are similar to what the exit numbers are on I-80 is just a coincidence.)