Prior to SH-23's establishment, the highway carried two designations—US-270 followed the same portion of the route that it does today, and a segment of SH-15 connected Elmwood to the Texas state line. (A connection with the current western terminus of SH-15 was made with what was then Farm to Market Road 1265 to Booker and TX-117 back to Oklahoma.) 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.