The major portion of the road is 12.5 miles (20.1 km) south from Chester Avenue to 135th Street / Missouri Route 150.

It continues as Eaton Street into Kansas City, Kansas at its northern terminus and as Kenneth Road into Leawood at its southern terminus.

Its northernmost point is roughly 0.75 miles (1.21 km) south of Interstate 35.

Three noncontinuous minor stubs, all within the West Bottoms district of Kansas City, Missouri, are also designated as State Line Road.

[3] Intermittent sections of rural road extend south of the Kansas City metropolitan area to Drexel (separating Miami County, Kansas, from Cass County, Missouri) though they are not considered part of State Line Road in local lexicon.