The new Irwindale was built in a city of 500 people, 99% industrial, next to a giant hole in the ground, and Fontana was built on condemned contaminated land from the old Kaiser steel plant. Both were about the only practical place for a race track, and both the dragstrips just happened to be there, in the far corner, cause of a decent sized parking lot for the roundy-round tracks.
And STILL they managed to disappear.
OCIR was sold to build a housing development (as was riverside) until they found out they couldn't build there because of the airport glide path. It's now just a weed covered field.... and has been for 40 years.