K-4 is the longest designated state highway in Kansas, at 369.079 miles (593.975 km). It begins north of Scott City at U.S. Route 83 (US-83) and travels eastward to US-59 near Nortonville in northeast Kansas. A segment of the highway in Saline County overlaps Interstate 135 (I-135) and US-81, and a section in Topeka runs concurrent with I-70. It also intersects several other major highways, including US-283 in Ransom, US-183 in La Crosse, US-281 in Hoisington, US-77 in Herington, I-470 and US-75 in Topeka, and US-24 northeast of Topeka.

U.S. Route 83 (US-83) is a part of the U.S. Highway System that runs from the Veterans International Bridge in Brownsville, Texas north to the Canadian border, north of Westhope, North Dakota, where it continues as Manitoba Highway 83. In the U.S. state of Kansas, US-83 is a main north–south highway that runs from the Oklahoma border north to the Nebraska border.