From what I've seen in the DFW area, there were many "formerly on the fringes" salvage yards from the '60s that were enveloped into population growth areas. An observed scenario, many times over. Even if some were in a less-valuable part of town (one in Dallas, in particular), the land eventually became too valuable AND the long-time owners took their "windfall" offer for the land, AND went on to do something else in their later years.
There was an old-line salvage yard near me and my work. I found many parts there. The owner would give me the key to the back lot, to get in, and I'd put everything in heavy plastic bags, and show him what I'd gotten. He tell me ang price and I'd pay up. Quite FUN!
He had to put concrete on top of the ground to meet/mitigate the ground contamination issues (old oil leaking from the cars and such). When those paths were covered, then he had to move the cars onto them and do the remaining exposed soil. The concrete was "rough poured", but it made the yard much more "all weather", too.
The yard was located on the west side of an emerging municipality and on the east side of the "main town", so he was caught in the middle. Obviously, the yard could have possibly been grandfathered-in, but when the owner passed away, his son let things settle down and then the yard was put up for sale. Being purchased by one of their good friends and the place is now under development.
End result, it takes more time to find older salvage yards and more time to get to them. Their numbers are dwindling, unfortunately. Several years ago, a Buick-only yard in Carrier, OK sold out and crushed out. BUT interested people were advised of this well before it happened. Which gave the customers a chance to build a shopping list and get it done. Increased land prices, no interest in keeping things going by the/any offspring, and owner retirement are usually key factors in these deals.
There are still some older yards in a 100-200 mile radius of DFW. Most have been there for years. Off the beaten path a bit.
The OTHER issue is the rise of the repro parts business, but usually for "popular" cars. Some of the older yards have branched out into Internet sales to stay alive. Which makes people like Murray Park even MORE valuable to our Chrysler-oriented hobby!
We usually never like to see automotive memories become crushed sheet metal, but if the yard owner is more concerned about "weight" of the bodies, then the metal becomes a mere commodity, whose value can rise and fall. When times get tough, many yards pick the less popular and heaviest vehicles to crush. A good yard, by comparison, keeps the inventory "turning" several times a year. Possibly, an even better dismantler will remove valuable items and resell them!
Enjoy!
CBODY67