not occur until the late 1910s and early 1920s when groups from Indiana, Minnesota, and Wisconsin began surveying road to develop signage standards. They reported their findings to the Mississippi Valley Association of Highway Departments, which adopted their suggestions in 1922 for the shapes to be used for road signs. These suggestions included the familiar circular railroad crossing sign and octagonal stop sign.

In January 1925, Thomas Harris MacDonald, chief of the federal Bureau of Public Roads,