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.

K-4 was first designated by KDOT in 1927, and at that time ran from K-1 (now U.S. Route 183) in La Crosse eastward to the Missouri state line by Atchison.

[3] From here, K-4 continues east as it serves the towns of Shields, Utica, Arnold, before reaching Ransom, where it intersects US-283.

[3][4] From La Crosse, K-4 heads due east, running through Otis as it approaches the Barton County line.

It runs just north of Marquette, which lies at the opposite end of the former K-175, before heading towards downtown Lindsborg.

In Lindsborg, K-4 encounters former US-81 Business, before heading north out of town and into Saline County.

The highway then bypasses Assaria to the west before heading north to spawn a child route, K-104, after which it turns due east once again.

[3][6] K-4 then curves southeast of Meriden (the former state route K-245 existed to connect the town to K-4 until dissolved in 2014[7]).

[8][9] Past Herington, K-4 continued east on US-50N (now US-56) to Council Grove, where it then followed a series of now unnumbered roadways to rejoin its present alignment at Eskridge.

[9] K-4 remained on Topeka Boulevard north to an intersection with NE 82nd Street south of the Shawnee–Jackson county line.

[1][9] Past Valley Falls, K-4 followed 162nd Street and modern K-16 east to Osage Road, where the route intersected K-16.

At the time, K-4 and K-16 overlapped northward along Osage Road to Nortonville, then followed the modern alignments of US-159 and K-116 to Cummings.

In Atchison, K-16 split from K-4 and headed northward on modern K-7 while K-4 continued to the Missouri state line on current US-59.

[9] In a June 19, 1936 resolution, K-4 was realigned slightly within La Crosse, which eliminated a short overlap with K-1 (modern US-183).

[12] In an August 7, 1941 resolution, the highway was realigned to the south of Ransom, which eliminated two railroad crossings.

[13] In a separate August 7, 1941 resolution, K-4 was realigned from Shields northeastward to Pendennis to eliminate four sharp curves.

[15] In a June 5, 1946 resolution, K-4 was realigned slightly north by Otis to eliminate two railroad crossings.

[18][19] Before 1956, K-4 originally followed US-50N (now US-56) from Herington to Council Grove, then northeast along now locally maintained highways to Eskridge.

Then in a February 9, 1956 resolution, it was realigned to follow and replace K-10 to K-99, then continue east to meet its old alignment in Eskridge.

[22] In a February 25, 1959 resolution, K-4 was realigned between Meriden and Valley Falls to remove some dangerous curves.

Then in a December 4, 1963 resolution, it was realigned to continue south from Meriden to US-24, then followed US-24 west into Topeka.

Also at this time a short K-4 spur was created, and when extended was to become a new alignment of K-4 between Valley Falls and Nortonville.