Photo courtesy of Rich Piehl (taken August 2003)
Looking west on Missouri 100 at Interstate 44 in Franklin County, this sign assembly shows a couple of unusual characteristics. The obvious item is the designation of the supplemental route, AT. For whatever reason, Franklin County has an unusually high number of supplemental routes beginning with A (rather than using double letters): AB, AC, AE, AF, AH, AK, AM, and AN are other such routes in the county.
The less obvious characteristic is that the topmost marker is not the Interstate marker, which usually appears at the top of junction sign assemblies for routes intersecting an Interstate highway.