U.S. Route 81

U.S. Route 81 is one of the many 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 Canadian 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.

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 US-Canadian border to the US Mexican 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."