|Length||1,220 mi[ citation needed] (1,963 km)|
|Existed||1926, truncated northward in the 1990s[ citation needed]–present|
|South end||I-35W / US 287 at Fort Worth, TX|
I-40 at El Reno, OK
I-135 from Wichita, KS to Salina, KS
I-70 near Salina, KS
I-80 at York NE
I-90 at Salem, SD
I-29 from Watertown, SD to Manvel, ND
I-94 at Fargo, ND
US 2 at Grand Forks, ND
I-29 from Joliette, ND to Pembina, ND
|North end||I-29 / PTH 75 at Pembina–Emerson Border Crossing near Pembina, ND|
|States||Texas, Oklahoma, Kansas, Nebraska, South Dakota, North Dakota|
U.S. Route 81 is a major north-south highway that extends for 1220 miles in the central United States and is one of the earliest United States Numbered Highways established in 1926 by the US Department of Agriculture Bureau of Public Roads.
The route of US-81 follows that of the old Meridian Highway (so called because it roughly followed the Sixth Principal Meridian of the US Public Land Survey System) which dates back as early as 1911.  The highway has alternately (and unofficially) been known as part of the Pan-American Highway.  In the segment in the State of Oklahoma, the highway closely corresponds to the old Chisholm Trail for cattle drives from Texas to railheads in Kansas in the 1860s and 1870s.
As of 2004, the highway's northern terminus is just north of Pembina, North Dakota at the Canada–US border. At this point, it is routed along Interstate 29 and continues northward into Manitoba on Highway 75 that leads to Winnipeg.
Its southern terminus is in Fort Worth, Texas, at an intersection with Interstate 35W. Between the inception of the numbered highway system in 1926 through 1991, US 81's southern terminus was at the Mexican border in Laredo, Texas. In 1991, the terminus was moved to San Antonio. The route was shortened to its present length of 1,234 miles (1,986 km) in 1993, when the terminus was moved to Fort Worth. In both cases, the dropped portions of US 81 were replaced by Interstate 35.[ citation needed] Portions of former US-81 south of Fort Worth continue to exist as business loops of I-35; a section from Hillsboro to Fort Worth exists as State Highway 81.
The decommissioning of portions of U.S. 81 that have been displaced by concurrent Interstate highways means that U.S. 81 no longer extends from the Canada–US border to the Mexico—US border, while one of its "children", U.S. Route 281 does extend to both borders. As a result of decommissioning portions of US 81, the length of U.S. 81 is actually 672 miles shorter than of its "child."
US 81 at its inception in 1926 followed the route of State Highway 2, which began in Laredo and passed through San Antonio, Austin, Waco, and Fort Worth before passing over the Red River into Oklahoma four miles (6 km) north of Ringgold. The 1936 Official Map of the Highway System of Texas clearly shows the route labeled both as US 81 and S.H. 2. It was cosigned with U.S. Highway 83 for 18 miles (29 km) from Laredo to 2 miles (3.2 km) south of Webb, with U.S. Highway 79 for 18 miles (29 km) from Austin north to Round Rock, and with U.S. Highway 77 for 33 miles (53 km) from Waco to Hillsboro. In 1940 U.S. Highway 287 was extended south into Texas, and a 67-mile (108 km) stretch from Fort Worth northwest to Bowie was cosigned with US 81. The Summer 1941 Texas Highway Map shows this pairing, and the current southern terminus of US 81 is still cosigned with US 287.
The Spring and Summer 1949 Texas Highway Department Official Map designates the length of US 81 from Laredo to Fort Worth as part of the National System of Interstate Highways, but no numeric designation is given.
It was not until 1959 that parts of US 81 in Texas appeared on the Texas Official Highway Travel Map cosigned with Interstate 35 shields. Succeeding maps reflect the slow completion of I-35 and I-35W over the stretch of US 81 between Laredo and Fort Worth, with the 1978-79 Texas Official Highway Travel Map showing only a 14-mile (23 km) section from Encinal north to 3 miles (4.8 km) south of Artesia Wells as incomplete, and the 1980 Texas Official Highway Travel Map showing that section completed. In 1980, US 81 was cosigned with I-35 and I-35W except where the Interstate bypassed towns, with US 81 providing the main route through town and then reconnecting with I-35 on the other side. The longest section of US 81 in 1980 not cosigned with the Interstate ran from I-35 in Hillsboro 20 miles (32 km) north to I-35W, just north of Grandview.
Enid, El Reno, Chickasha, and Duncan are major Oklahoma towns on the highway; historically, the small town of Hennessey is notable. Among the elders throughout the small towns that are dotted along Route 81 in Oklahoma, the sixth meridian is commonly known among the locals as the "Indian Meridian" but Route 81 is not known as the "Indian Meridian Highway." The Indian Meridan is located some 40 miles (64 km) east and parallel of U.S. Route 81. By pure coincidence, the Chisholm Trail of the Post-Civil-War decades roughly followed along the corridor of present-day Route 81; the region was not opened for settlement until several years after the cattle drives were discontinued; cultural memory harkened exclusively for many years to Indian Meridian Highway until recognition of the old cattle trail grew in the late 1900s. 
Nearly all of US-81 in Kansas is either freeway or expressway. The route enters Kansas as a two-lane near Caldwell. From South Haven to Wichita it closely parallels Interstate 35, which is also known as the Kansas Turnpike in that area. After South Haven, the only town of any significance along US 81 until Wichita is Wellington, which is just west of the Turnpike along U.S. Route 160.
At Wichita, US-81 joins Interstate 135. The two highways remain joined until Salina, with I-135's mile markers taking precedence. Interstate 135 ends at Interstate 70 but US-81 continues as a freeway to Minneapolis, then as an expressway passing through Concordia before exiting the state north of Belleville.
The alignment of US-81 from Wichita to Salina prior to the completion Interstate 135 is fully intact. The prior alignment ran from where current US-81 breaks off for Interstate 135 at 47th street, north through Wichita along Broadway street. Old US-81 roughly parallels Interstate 135 to Newton. Ol US-81 follows current K-15 through Newton between an interchange with US-50 and Hesston Road, where old US-81 breaks northwest onto Hesston road. Old US-81 then travels through the small Kansas towns of Hesston, Moundridge, and Elyria, before turning to the north, and going through the town of McPherson as Main street. North of McPherson, old US-81 continues to Lindsborg, where it follows current K-4 until an interchange with Interstate 135. Old US-81 passes under Interstate 135 and continues to parallel it about 1/2 mile to the east. Old US-81 then travels through Assaria, where it encounters another brief overlap with K-4 and K-104. Old US-81 continues through the city of Salina as Ninth street. North of Salina, Old US-81 encounters brief overlaps with K-143 and K-18. Old US-81 follows K-106 to an interchange with current US-81, where the two alignments are joined back together.
From Salina to the Nebraska state line, the highway is named the Frank Carlson Memorial Highway, in honor of the late Senator Frank Carlson. Senator Carlson was a native of Concordia who represented Kansas in the U.S. Senate from 1951-1969. Before serving in the Senate, he was Governor of Kansas from 1947–1950.
U.S. 81 enters Nebraska as an expressway at Chester and continues as an expressway to York, where the highway intersects Interstate 80. After a two-lane section going north from York and an overlap with Nebraska Highway 92, U.S. 81 again becomes an expressway at Nebraska Highway 64. This expressway section passes through Columbus and Norfolk. North of Norfolk, U.S. 81 is a two-lane, undivided highway which passes through no towns before exiting the state in Cedar County.
U.S. 81 enters South Dakota by a Missouri River crossing, via the Discovery Bridge at Yankton. Its junction with Interstate 90 is south of Salem. U.S. 81 passes near Madison before it joins with Interstate 29 at Watertown. The two highways remain concurrent through the rest of the state, leaving South Dakota near New Effington.
U.S. 81 enters North Dakota concurrently with Interstate 29. It is paired with I-29 from the South Dakota border, passing through Fargo, to the north side of Grand Forks. There it splits off to the northwest, passing through the city of Manvel. It parallels I-29, passing through the town of Grafton before joining North Dakota Highway 5 near Cavalier. It rejoins I-29 and continues to the US–Canada border at Pembina. The original route of US 81 survives as North Dakota Highway 127 and 'County Road 81' in Richland, Cass, Traill, and Grand Forks counties.
US 81 started out as the Meridian Highway, an auto trail organized in 1911 to connect Winnipeg, Manitoba, Canada, to the Gulf of Mexico near the Sixth Principal Meridian.  The southern terminus, initially at Galveston,  was later moved to Laredo, where it would connect with a proposed extension to Mexico City (later built as part of the Pan-American Highway).  Five of the six states along the route assigned a single number to the highway, mostly changing at the state line. ( Kansas did not number its highways until 1926.)   Planning to replace these designations — and the Meridian Highway name — began in 1925, when the Joint Board on Interstate Highways created a preliminary list of interstate routes to be marked by the states;  the entire Meridian Highway was assigned Route 81.  The new number was officially adopted in late 1926.  
The Interstate Highway System was approved in 1956, and included several routes that would replace much of US 81. Interstate 35 followed the corridor from Laredo north to Wichita, where I-35 turned northeast towards Kansas City, with a branch - Interstate 35W - continuing parallel to US 81 to Salina, Kansas. Between Fort Worth, Texas and South Haven, Kansas, I-35 did not directly replace US 81, instead following U.S. Route 77 through Oklahoma City, but replaced it as a long-distance highway. From Salina north through Nebraska, the US 81 corridor was not part of the Interstate system, but Interstate 29 began at Kansas City, gradually heading northwest and intersecting US 81 at Watertown, South Dakota, then following it north to the Canada–US border. The portion through northern Kansas and Nebraska remains an important regional corridor, but by the late 1970s, the rest had been mostly replaced by I-35 and I-29 for non-local traffic.  The American Association of State Highway and Transportation Officials approved a truncation in 1991, changing the southern terminus from Laredo to north of Fort Worth and removing long overlaps with and short sections parallel to I-35. 
Business US 81 in San Antonio, Texas was replaced by Loop 368 and Loop 353. The north side (Loop 368) traveled down Broadway & Austin Highway while the south side (Loop 353) was Nogalitos & Laredo Highway. When it was replaced, they renamed the street New Laredo Highway.
Old portions of US 81 in various parts of North Dakota are now county routes. The current US 81 in these areas is co-signed with Interstate 29.
Completion of the four-lane section of U.S. 81 between Salina and Minneapolis, Kansas occurred in 1971. 
Between Wichita and Salina, Kansas, old sections of US-81 are now county routes and short sections of state highways. The current US-81 in this area is co-signed with Interstate 135. In McPherson County, the old alignment of US-81 is signed as Business US-81.
Old US 81 was the site of one of several shooting incidents committed by 38-year-old Cedric Larry Ford, which culminated in a mass shooting at an Excel Industries building in Hesston, Kansas that killed three and injured twelve. 
- I‑35W / US 287 in Fort Worth. US 81/US 287 travels concurrently to Bowie.
- US 380 in Decatur
- US 82 in Ringgold
- US 70 in Waurika
- US 277 in Ninnekah. The highways travel concurrently to Chickasha.
- I‑44 in Chickasha
- US 62 / US 277 in Chickasha. US 62/US 81 travels concurrently through Chickasha.
- I‑40 in El Reno
- US 60 / US 412 in Enid. US 60/US 81 travels concurrently to Pond Creek.
- US 64 in Enid. The highways travel concurrently to west of Pond Creek.
- US 177 in South Haven
- US 166 north of South Haven
- US 160 in Wellington. The highways travel concurrently through Wellington.
- I‑135 in Wichita. The highways travel concurrently to northwest of Salina.
- I‑235 in Wichita
- US 54 / US 400 in Wichita
- I‑235 in Wichita
- US 50 in Newton. The highways travel concurrently to northeast of Newton.
- US 56 in McPherson
- I‑70 / I‑135 / US 40 northwest of Salina
- US 24 northeast of Delphos
- US 36 in Belleville
- US 136 south-southeast of Hebron
- US 6 in Fairmont
- I‑80 in York
- US 34 in York. The highways travel concurrently to north of York.
- US 30 south of Columbus. The highways travel concurrently to Columbus.
- US 275 in Norfolk
- US 20 southeast of McLean
- South Dakota
- US 18 south of Freeman
- I‑90 south of Salem
- US 14 south of Arlington. The highways travel concurrently to Arlington.
- US 212 in Watertown
- I‑29 northeast of Watertown. The highways travel concurrently to east of Manvel, North Dakota.
- US 12 northwest of Summit
- North Dakota
- I‑94 / US 52 in Fargo
- US 10 in Fargo
- US 2 in Grand Forks
- I‑29 south-southwest of Joliette. The highways travel concurrently to the Canada–United States border north of Pembina.
- I‑29/ PTH 75 at the Canada–United States border north of Pembina
Though it did in the past, US 81 currently does not connect to either of its spur routes.
- Transcript - The Meridian Highway
- Highway 81
- "Retracing the Chisholm Trail". Red River Historian. Retrieved 7 February 2018.
- "South Dakota Codified Laws". Legis.state.sd.us. Retrieved 2013-01-26.
- Nebraska State Historical Society, The Meridian Highway: From Canada to Mexico, accessed October 2007
- Fort Wayne News, Good Roads Enthusiasts Prepare for Second National Convention, February 4, 1913
- Los Angeles Times, Plan Highway from Laredo Across Mexico, March 22, 1920, p. I5
- Rand McNally Auto Road Atlas, 1926, accessed via the Broer Map Library
- The following routes were used, shown on the 1926 Rand McNally:
- Texas: 2
- Oklahoma: 2
- Kansas: state highways were not numbered prior to the U.S. Highway system
- Nebraska: 4 ( Lincoln Star, Road Conditions, October 11, 1925)
- South Dakota: 21
- North Dakota: 1
- Richard F. Weingroff, From Names to Numbers: The Origins of the U.S. Numbered Highway System
- Report of Joint Board on Interstate Highways, October 30, 1925, Approved by the Secretary of Agriculture, November 18, 1925
- Bureau of Public Roads & American Association of State Highway Officials (November 11, 1926). United States System of Highways Adopted for Uniform Marking by the American Association of State Highway Officials (Map). 1:7,000,000. Washington, DC: U.S. Geological Survey. OCLC 32889555. Retrieved November 7, 2013 – via University of North Texas Libraries.
- United States Numbered Highways, American Highways ( AASHO), April 1927
- Gulf, Tourgide: United States, Canada and Mexico ( Rand McNally & Company), 1977
- Texas Department of Transportation, Highway Designation File: U.S. Highway No. 81, accessed October 2007
- Southeast Nebraska Tourism Council. "Pan American Highway...Gateway to Southeast Nebraska" 2002 Southeast Nebraska Visitor's Guide. Page 80.
- Spurney, Blake (February 25, 2016). "Update: 9 PM Press Conference On Hesston Shooting". The Hesston Record. Archived from the original on March 2, 2016. Retrieved February 26, 2016.
|Browse numbered routes|
|← SH 80||TX||SH 81 →|
|← SH-80||OK||SH-82 →|
|← K-80||KS||K-82 →|
|← I-80||NE||US 83 →|
|← SD 79||SD||US 83 →|
|← ND 73||ND||US 83 →|