U.S. Route 81 (US-81) is a part of the U.S. Highway System that travels from Fort Worth, Texas to the Pembina–Emerson Border Crossing near Pembina, North Dakota.

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.

The two highways remain joined until Salina, with I-135's mile markers taking precedence.

[4] The alignment of US-81 from Wichita to Salina prior to the completion Interstate 135 is fully intact.

This plan was later cancelled in a March 29, 1961 meeting, when US-81 was realigned onto I-35W to current exit 72, then west along the proposed K-155 (modern Smoky Valley Road) to the old US-81 alignment.

It goes west on Kansas Ave. for about two miles (3 km) in a concurrency with US-56 and turns south on Main Street for 2 miles (3.2 km), passing Central Christian College and National Cooperative Refinery Association.

At K-61, it exits east in a 2 miles (3.2 km) "wrong-way" concurrency with K-61 before ending at I-135 and US-81 southeast of McPherson.

It shared a 4 miles (6.4 km) concurrency with K-4, which turns to the west in south Lindsborg.