Adding to my earlier review there is a question as to where do the arrows point. Here is a good link that provides more info and other links for those wishing to check these concrete arrows out.
http://www.messynessychic.com/2013/11/15/the-forgotten-giant-arrows-that-guide-you-across-america/
I would answer the question by saying they are more like giant push pins in your Google travel map pointing ahead to the next arrow and beacon on your route, it could be west from NYC to SAN or ABQ to PHX.
Arrows Across America - I drove my daughter from Las Vegas to FL in 2017 and we took in the arrows. The museum at Grants-Milan airport is fine, but the arrow there is a reproduction. So we had to venture on to where we could locate one off of a road. We located one north of Cuervo NM. Well the road was dirt and wash-board and it took 15 minutes for five miles but we thought the adventure was worth it. If you are doing Route 66, definitely add this in to your trip.