Interesting, always associated the atco track with the large dirt oval with ends almost touching the Old WH pike and Burnt mill.
Seeing the pic showing asphalt had me back googling maps, I never would have known that was there!
I know its a little outside the Pine Barrens, but does anyone know about the racetrack in East Brunswick, Middlesex County? It was on Racetrack Road (aptly named) and appears abandoned in the 1931, 1940, and 1947 aerials. There is a supermarket and housing there now, but no signs of the track except the name of the road. This would have been an early track if it was abandoned by 1931, so I wonder if it was a horse racing track.
I gave my auto/racing library to the International Motor Racing Research Center at Watkins Glen. Included was a book that listed all the auto racing tracks that have existed in each of the United States, with data on each including dates of operation. You might call the IMRRC, ask for Bill Green, (607-535-9044), their historian, use my name as we're OLD friends. Bill might have other information that will at least tell you if it was an auto or horse track. Another approach would be to go to the Township or County tax office, lookup the current deed info, and then go to the Clerk's office and track the deed/s back. There's the chance that, the track might have been privately owned, on someone's farm and the deed wouldn't reflect its use.