You might think this photo shows one of the wide-style markers for three-digit highways that came into use in Missouri starting in 2000. However, the absence of a white border on the US 136 marker indicates that it's one of the wide markers that occasionally were found near freeways before 2000. The current style of wide markers can be seen about three miles to the east, at the intersection of US 136 and Missouri 146.
This photo was taken in July 2002.