History is all around us. You don't have to look hard but you do have to look around. Within a mile of my home are two rare Illinois 15D cement road markers. What was 15D? It was part of the state gasoline tax code that stipulated once a county built concrete highways--they would be maintained by the state.
This post is on Niles Center Road just north of Main Street in Skokie, Illinois. It was placed there in 1925 and it survives probably because it stands right next to a telephone pole--the markers aren't easy to see and they are road hazards--even if they are not on the road.
Rare 15D road marker in Morton Grove