U.S. Route 20

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

Question: What's the longest highway in the US?