 The connection to Kansas north of US-64 did not exist as a state highway prior to 1957; it first appears on the 1958 state highway map, also signed as SH-15.The highway is not shown as overlapping US-64 and US-270 to Elmwood.SH-23 is first shown replacing SH-15 on the 1959 map, implying the change took place in 1958.