Old Highway 80 runs alongside I-8 near Felicity. I spotted one of several "C" blocks off the side of the road.
These concrete monuments stood about 6 inches above ground and were placed along the right-of-way boundaries on state routes beginning in 1914 and ending in ending in 1934. Following these "C" block markers you can actually track the original road bed.
It's pretty cool to see these markers still sitting there after all these years.