Question: What is the longest highway in the U.S.?

U.S. Route 20



U.S. Highway 20 (US20) is an east–west United States highway that stretches from the Pacific Northwest all the way to New England. The "0" in its route number indicates that US20 is a coast-to-coast route. Spanning 3,365 miles (5,415km), it is the longest road in the United States,[1] and particularly from Newport, Oregon  to Boston, Massachusetts, the route is roughly parallel to that of the newer Interstate 90 (I-90), which is in turn the longest Interstate Highway in the U.S. There is a discontinuity in the official designation of US20 through Yellowstone National Park, with unnumbered roads used to traverse the park.
It and US30 break the general U.S. Route numbering rules in Oregon, since US30 actually starts north of US20 and runs parallel to the north throughout the state. The two run concurrently and continue in the correct positioning near Caldwell, Idaho. This is because US20 was not a planned coast-to-coast route while US30 was. US20 originally ended at the eastern entrance of Yellowstone Park; it was extended in 1940.[1]
The highway's eastern terminus is in Boston, Massachusetts, at Kenmore Square, where it meets Route 2. Its western terminus is in Newport, Oregon, at an intersection with US101, within a mile of the Pacific Ocean.[3]
Route description
The highway passes through the following states:
Oregon


US20 begins at an intersection with US101 in Newport, Oregon, and runs generally eastward towards Idaho. On the way it goes over the Central Oregon Coast Range, through several Willamette Valley cities including Corvallis and Albany, climbs the Cascade Mountains over Santiam Pass, goes through Bend, and traverses the Oregon High Desert passing through Burns. It eventually overlaps with US26 in Vale, and the two roads continue concurrently to the Idaho border.
Idaho

US20 crosses into Idaho from Oregon northwest of Parma. It runs concurrently with US26 and joins US95 through Parma. US20/US26 leaves US95 southeast of Parma and runs to Caldwell where US20/US26 joins with I-84 and US30 for a short time. These four highways parallel each other (on two roadways) to Boise where US20/US26 runs through downtown before joining with I-84 and US30 again to Mountain Home, where it departs at exit95 to head east, past Rattlesnake Station, Anderson Ranch Dam road, and cresting at Cat Creek summit at 5,527 feet (1,685m) above mean sea level. It continues into and across Camas County through Fairfield to Timmerman Junction, the intersection in Blaine County with State Highway 75, the route to Sun Valley, Galena Summit, and Stanley. US20 continues east through Picabo and Carey, joined with US26 and US93, to Craters of the Moon and Arco, where US93 splits off and turns north-northwest to climb the Big Lost River valley. US20/US26 continues on through the Idaho National Laboratory, where the highways split just west of Atomic City; US26 heads to Blackfoot and US20 to Idaho Falls, where it turns north-northeast to pass near Rexburg as a freeway. US20 then climbs through the communities of St. Anthony, Ashton, and Island Park, and crosses the Continental Divide at Targhee Pass at 7,072 feet (2,156m), entering Montana west of West Yellowstone.
Montana

In the state of Montana, US20 runs for less than 10 miles (16km). It runs from the Idaho state line to West Yellowstone, Montana, the western entrance to Yellowstone National Park. US20 is known as the Targhee Pass Highway in Montana.
Wyoming
In the state of Wyoming, the eastern segment of US20 starts at the eastern entrance to Yellowstone National Park along with the western termini of US14 and US16. These three routes run east to Greybull, where US14 continues east and US16/US20 turns south; at Worland, US16 turns east while US20 continues south, passing through Wind River Canyon south of Thermopolis. US20 joins US26 in Shoshoni, where it turns east. In Casper it joins I-25 and US87. These four routes stay combined to Orin, where US20 turns east. At its intersection with I-25, US18 begins. US18 and US20 are concurrent from Orin to Lusk. US18 separates there and US20 runs east into Nebraska.
Nebraska



In the state of Nebraska, US20 runs from west of Harrison to South Sioux City on the Missouri River. Portions overlap US385, US83, US183, US275, I-129, and US75.
Iowa


US20 enters Iowa at Sioux City via the Missouri River crossing with I-129 and US75. After skirting the southeast side of Sioux City as a freeway with US75, US20 continues east as an expressway to Moville. From Moville through north of Early at the junction with U.S. Route 71 and Iowa Highway 471, US20 was reconstructed from a rural two-lane highway to a four-lane road. This segment re-opened October 19, 2018 and made it so that US20 is a continuous four-lane highway during its entire time in Iowa. Passing north of Early, Iowa and Sac City, where it has another interchange with the realigned U.S. Route 71, then passing to the south of Fort Dodge and Webster City before intersecting I-35 near Williams.
A new segment of freeway between US65 south of Iowa Falls and Iowa Highway 14 opened in 2003 creating a continuous four-lane route from Moorland to Dubuque. The new segment shaved 16 miles (26km) off US20's length in Iowa. In the Waterloo/Cedar Falls area, the segment of US20 overlapped by the Avenue of the Saints, which is also designated as Iowa Highway 27. US20 passes Independence, Manchester, and Dyersville before reaching Dubuque. At Dubuque, US20 crosses into Illinois over the Julien Dubuque Bridge.
Illinois


In the state of Illinois, US20 begins in East Dubuque, following southeastward along the Mississippi River, and continues into the very hilly Driftless Area of northwest Illinois through Galena and Elizabeth. The highway then transitions eastward from the Driftless Area to the Interior Plains near Stockton. The road continues as a bypass north of Freeport, and then runs as a freeway along the southern fringe of Rockford. From Rockford to Chicago, Illinois, US20 is a mixture of four-lane expressway, four-lane limited access freeway, and winding two-lane surface road. It is signed as "General U.S. Grant Highway" after Ulysses S. Grant. U.S. 20 runs through the south side of Chicago as 95th Street. US20 exits Illinois along with US12 and US41 as Indianapolis Boulevard south of the Chicago Skyway.
Indiana



In the state of Indiana, US20 enters from the west beneath the Chicago Skyway with US12 and US41. US20 passes through heavily industrialized northwestern Indiana and is the main east–west artery through Gary. It then parallels US12 to just west of Michigan City before running due east to South Bend. US20 travels around South Bend and Elkhart on the St. Joseph Valley Parkway, a four-lane limited access freeway, then returns to surface road east of Elkhart. US20 then passes through LaGrange and Angola, intersecting with I-69 before leaving Indiana just north of the eastern terminus of the Indiana Toll Road.
From Gary to South Bend, US20 was built as the Dunes Relief Road. During the 1930s and 1940s the Dunes Highway, US12, was becoming more crowded as housing lots and communities developed in the Indiana Dunes. Today, there are numerous communities along US20 and the lakefront, including Gary, Portage, Burns Harbor, Porter, Chesterton, Pines, and Michigan City.
Most notably, the route is one of the main access roads to the Indiana Dunes National Lakeshore.
Ohio


US20 enters Ohio from Indiana just west of Columbia and traverses east through Pioneer and Alvordton to Fayette. It continues east through Oakshade, Assumption and becomes five-lane, non-limited access roadway into Sylvania to Toledo, and then turns south until into the Toledo suburb of Maumee. After Maumee, US20 crosses Maumee River curving back east becoming 2 lanes through Perrysburg to Woodville, where it becomes a four-lane, non-limited access highway. It bypasses Fremont while concurrent with US6, State Route 53, and State Route 19, and then travels through the northern edge of Clyde and the downtown area of Bellevue, where it is joined by State Route 18. From there the four-lane highway continues through Monroeville and bypasses Norwalk, then becomes a two-lane highway from there to Oberlin. Continuing east, US20 traverses through Elyria, North Ridgeville, Westlake, Rocky River, Lakewood and Cleveland, where it goes right through Public Square. East of Cleveland US20 follows the southern shore of Lake Erie, following Euclid Avenue from Public Square, and traverses Euclid, Wickliffe, where it intersects with I-90, Mentor, Painesville, Madison, Geneva, Ashtabula and crosses into Pennsylvania just east of Conneaut.
Pennsylvania


US20 runs for nearly 50 miles (80km) across Erie County, Pennsylvania, most of that time just south of the CSX Amtrak railroad tracks. US20 appears as West Ridge Road eastward from the Ohio border through Springfield, Girard, Fairview and Millcreek townships. At the intersection with Pennsylvania Route 832, just outside the Erie city limits, it becomes West 26th Street. After it reaches city center at the intersection with State Street, it becomes East 26th Street. It turns sharply northward as Broad Street at the Bayfront Connector, then turns east again as Buffalo Road through Wesleyville and Harborcreek Township. Buffalo Road turns sharply northward at the town of Harborcreek. US20 intersects with Pennsylvania Route 955 and resumes its eastward journey. At North East Township, US20 becomes West Main Road. Within the town limits, it becomes West Main Street until it reaches the town center at its intersection with Pennsylvania Route 89, where it becomes East Main Street. Outside the town limits it becomes East Main Road until it reaches Pennsylvania's border with New York.
New York


In New York, US20 runs roughly parallel to the New York State Thruway (I-90) throughout the state. The route runs concurrently with New York State Route 5 twice, with the second overlap extending 68 miles (109km) across Western and Central New York from Avon to Auburn. US20 runs across the rural Cherry Valley Turnpike between Skaneateles and Albany. US 20 was also known as the Boston-Buffalo highway prior to the construction of the New York Thruway and Massachusetts Turnpike.
Massachusetts


In Massachusetts, US20 runs near I-90 Mass Pike, intersecting it at exits2 and 10A.
In part of Berkshire County, US20 runs north–south as it shares the roadway with US7. It is known as "Jacob's Ladder" as it crosses the Berkshire Hills between Lee in Berkshire County and Chester in Hampden County. From Chester to Westfield, US20 and the Boston and Albany Railroad follow the Westfield River down to the broad valley of the Connecticut River.
In Shrewsbury, US20 is called "Hartford Turnpike." In Northborough, and Worcester it is called "Southwest Cutoff", until it merges with the original Boston Post Road in Northborough (Southwest Cutoff and West Main Street). Southwest Cutoff was created at the turn of the century to bypass truck traffic around Shrewsbury center as well as connecting to the Boston and Worcester Turnpike.
In parts of eastern Massachusetts, US20 follows the route of the old Boston Post Road and passes by Longfellow's Wayside Inn, in Sudbury, the oldest continually operated Inn in America. In 1926, after engineers determined that heavy truck traffic on the Boston Post Road was damaging the foundations of the Inn, Henry Ford, then owner & proprietor, ordered the construction of the mile-and-a-half-long Route 20 bypass. Upon its completion on December 11, 1928, he sold it to the Commonwealth of Massachusetts for $1 and never cashed the check. According to the Boston Herald the by-pass cost Ford $288,000.[4] The original route of US20 is now called Wayside Inn Road.
US 20 continues from Sudbury through Wayland, Weston, Waltham, Watertown and then into Boston through Allston and Fenway–Kenmore. U.S. Route 20's official eastern terminus is in Kenmore Square at the intersection of Commonwealth Avenue, Beacon Street, and Brookline Avenue, where the alignment becomes Massachusetts Route 2. Route 2 continues for a short distance where it terminates at U.S. Route 3.

History
 Before the U.S. Highway System, the route in New England and New York was designated as New England Interstate Route 5 (NE-5), part of the New England Interstate Route system that existed between 1922 and 1927. Around 1923, from Springfield to Pittsfield, NE-5 was known as "Jacob's Ladder",[5] and from Boston to Albany, the "Hubway". When US20 was first commissioned, it took over the entirety of NE-5.
Historic termini
Until 1940, the western endpoint of US20 was the east entrance to Yellowstone National Park.
Historic routes
Between Fort Dodge, Iowa, and Dubuque, Iowa, the route has been upgraded to four lanes, the last link of this completed in 2003. Much of the old route is a few miles north of the present route except between I-35 and Waterloo. There, the old route is farther north, going through Iowa Falls, Aplington, and the north side of Cedar Falls along what is now Iowa Highway 57.
From just west of South Bend, Indiana, to the St. Joseph– Elkhart county line, the old route of US20 through St. Joseph County is now Business US20. In Elkhart County, its old route is now classified as a county road and is simply called Old US20. The St. Joseph Valley Parkway is the present route of US20 in the South Bend– Elkhart Area.
From 1930 to 1933, US20 followed what are now Massachusetts Route 67 and Massachusetts Route 9 from Worcester to Palmer via Shrewsbury and Northborough.[6]
The 1953 Massachusetts Department of Public Works Master Plan would have relocated US20 between Palmer, Massachusetts and either West Springfield, Massachusetts or Westfield, Massachusetts along the right-of-way now used by the Massachusetts Turnpike, but this was never implemented.[7]
Until 1970–72,[6] US20 followed an old route through downtown Springfield—Boston Road and State Street—crossing the Connecticut River via the older Memorial Bridge (now Massachusetts Route 147). The construction of I-291 prompted a change. US20 now crosses from West Springfield at the North End Bridge, and is co-signed with I-291 until Page Boulevard, where it heads back to Boston Road via the former route of 20A.

In 2012, the Historic US Route 20 Association was formed to identify, promote and preserve the history of the route and original alignments that were once signed "Route 20" from Boston to Newport.[8]
Historic names
The portion of US20 eastward from Illinois generally follows the path of the Yellowstone Trail.
In Massachusetts, US20 follows the Boston Post Road in Wayland and Sudbury.
In the state of New York, part of US20 follows the old Cherry Valley Turnpike and is still referred to by that name in some places.
From Buffalo westward to Cleveland, Ohio, US20 follows the path of the Buffalo Stage Road.[9]

Between Fremont, Ohio and Perrysburg, Ohio, the road dates back to the late 1830s. It was known then as the Maumee and Western Reserve Road. Nicknamed "Mud Pike" and earned a reputation as "The worst road on the continent" for the mudholes that would trap wagon wheels and slow draft animals. Travelers sometimes would take three days to travel 1 mile (1.6km). It is still signed as Maumee St. in and near Angola, IN.
Through western Indiana, US20 was built as the Dunes Relief Road, as it bypassed the heavily traveled Dunes Highway.
Northwest of Chicago it is called Ulysses S. Grant Highway.
Major intersections
Western segment
Oregon
US101 at West Olive Street in Newport
I-5 in Albany
US97 in Bend
US395 in Riley. The highways travel concurrently to northeast of Burns.
US26 in Vale. The highways travel concurrently to Mountain Home, Idaho.
Idaho
US95 north of Parma. The highways travel concurrently to southeast of Parma.
I-84 / US30 north of Caldwell. The highways travel concurrently to Caldwell.
I-184 in Boise. The highways travel concurrently through the city.
I-84 / US30 in Boise. The highways travel concurrently to Mountain Home.
US26 / US93 in Carey. US20/US26 travel concurrently to northwest of Atomic City. US20/US93 travel concurrently to Arco.
I-15 in Idaho Falls. The highways travel concurrently through the city.
Montana
US191 / US287 at Firehole Avenue in West Yellowstone. The highways travel concurrently to West Thumb.
Wyoming
US89 north-northwest of West Thumb. The highways travel concurrently to West Thumb.
Eastern segment
Wyoming
US14 / US16 at the East Entrance to Yellowstone National Park, southeast of Pahaska Tepee. US14/US20 travel concurrently to Greybull. US16/US20 travel concurrently to Worland.
US310 west-northwest of Greybull
US26 in Shoshoni. The highways travel concurrently to Orin.
I-25 / US87 at Events Drive on the Casper–Hartrandt city line. I-25/US20 travel concurrently into Casper proper. US20/US87 travel concurrently to Orin.
I-25 in Casper
I-25 southeast of Glenrock. The highways travel concurrently to Orin.
I-25 / US18 / US26 / US87 in Orin. US18/US20 travel concurrently to Lusk.
US85 in Lusk. The highways travel concurrently through the town.
Nebraska
US385 west of Chadron. The highways travel concurrently to Chadron.
US83 in Valentine. The highways travel concurrently to south-southeast of Valentine.
US183 west-northwest of Long Pine. The highways travel concurrently to Bassett.
US281 in O'Neill. The highways travel concurrently through the city.
US275 / US281 in O'Neill. US20/US275 travel concurrently to southeast of Inman.
US81 west-southwest of Randolph
I-129 / US75 / US77 in South Sioux City. I-129/US20 travel concurrently to Sioux City, Iowa. US20/US75 travel concurrently to the Woodbury–Concord township line.
Iowa
I-29 / I-129 in Sioux City
US59 in Holstein. The highways travel concurrently to southeast of Holstein.
US71 in Boyer Valley Township.
US169 in Elkhorn Township
US69 in Liberty Township
I-35 in Rose Grove Township
US65 in Ellis Township
US63 in Waterloo
I-380 / US218 in Waterloo. I-380/US20 travel concurrently to Poyner Township.
Illinois
I-39 / US51 in Rockford. The highways travel concurrently to Cherry Valley.
I-90 north-northeast of Hampshire
I-355 in Addison
I-290 in Elmhurst. The highways travel concurrently through the city.
US12 / US45 on the Stone Park-Melrose Park city line. US12/US20 travel concurrently to East Chicago, Indiana. US20/US45 travel concurrently to west of the Palos Hills-Hickory Hills city line.
I-290 on the Bellwood-Hillside-Westchester city line
US34 in La Grange
I-55 on the Countryside-Hodgkins city line
I-294 in Willow Springs
I-294 on the Hickory Hills-Bridgeview city line
US41 in Chicago. The highways travel concurrently to Whiting.
Indiana
I-90 northwest of Whiting
US12 on the Hammond-Gary city line. The highways travel concurrently into Gary proper.
I-65 in Gary
I-90 in Gary
I-94 in Burns Harbor
US421 in Michigan City
I-94 east-southeast of Michigan City
US35 east-southeast of Michigan City
US31 in South Bend. The highways travel concurrently through the city.
US33 in Elkhart
I-69 in Jackson Township
Ohio
US127 in Mill Creek Township. The highways travel concurrently to Gorham Township.
I-475 / US23 in Sylvania
I-80 / I-90 in Maumee
US24 in Maumee
I-75 / US23 in Perrysburg. US20/US23 travel concurrently to the Troy-Woodville township line.
US6 in Sandusky Township. The highways travel concurrently to Fremont.
US250 in Norwalk
US6 in Lakewood. The highways travel concurrently to Cleveland.
US6 / US42 / US322 / US422 in Cleveland. US20/US422 travel concurrently for one block.
US6 in East Cleveland. The highways travel concurrently to Euclid.
I-90 on the Euclid-Wickliffe city line
Pennsylvania
US6N in Springfield Township
I-79 in Erie
US19 in Erie
I-90 east-northeast of North East
New York
I-90 in Hanover
I-390 east of Avon
I-81 south-southwest of LaFayette
US11 south of LaFayette
I-87 in McKownville
US9W in Albany
US9 in Albany. The highways travel concurrently to Schodack.
US4 in East Greenbush
I-90 in Schodack
Massachusetts
US7 in Pittsfield. The highways travel concurrently to Lenox.
I-90 in Lee
US202 in Westfield. The highways travel concurrently through the city.
US5 in West Springfield
I-91 in Springfield
I-291 in Springfield. The highways travel concurrently through the city.
I-84 in Sturbridge
I-395 / I-290 in Auburn
I-495 in Marlborough
I-95 in Waltham
Route2 in Boston
See also


Massachusetts Route 20A
U.S. Route 20A in New York
U.S. Route 20A in Ohio
U.S. Route 20 Business—Sioux City, Iowa; also passes through South Sioux City, Nebraska
U.S. Route 20 Business—Fort Dodge, Iowa
U.S. Route 120, became Pennsylvania Route 120 in 1967
U.S. Route 220
U.S. Route 320 (now decommissioned, was part of the old Route 26)
U.S. Route 420 (part of U.S. Route 14 Alternate)


Further reading






 by Michael G. Buettner, February 2006
 at Empire State Roads
: August 11, 2006, article in The New York Times Escapes section.
 for photos taken along US20
 at USends.com
—book about US20
 Site dedicated to the preservation and promotion of Historic US Route 20