MN 40 serves as an east–west route between Madison and Willmar in west-central Minnesota.

The route is also known as: MN 40 crosses Lac qui Parle Lake west of Milan.

Lac qui Parle State Park is located seven miles (11 km) south of the junction of MN 40 and US Highway 59 (US 59) at Milan.

The section of the route between US 75 at Madison and the South Dakota state line was authorized c.

[citation needed] In 2009, its eastern terminus was moved from US 12 in Willmar to CSAH 5 (30th Street SW).