On May 17, 1938, both Kansas and Oklahoma renumbered K-11 and OK-48 respectively to bear the number "99", providing continuity between the states. At this time, SH-99 followed the same basic corridor of the present-day route from Madill north to Kansas. However, SH-48's designation was still in use from May 1938 to February 1941. The SH-48 designation was then made into the route passing through Konawa, which the SH-99 designation bypassed. After SH-48 was discontinued, however, it would only remain discussed for just under three years, SH-48 resurfacing for a route only east of SH-99. The portion of SH-48 from SH-99 to Konawa would later become part of SH-39.