Just outside Tucson, Arizona, the Pima Air & Space Museum is now the third largest air museum in the U.S. It's a fairly recent thing--opening in 1976--and was a natural development and outgrowth from the storage site at Davis Monthan, just across the street. It's natural, therefore, that the bulk of airplanes in the museum are military based (although certainly not all of them).
The Davis-Monthan Air Force Base 309th AMARG (Aerospace Maintenance and Regeneration Group) was established just after World War 2. It is often called the "bone yard", but it actually does more than simply store old airplanes. It's useful to know that you won't find stored aircraft that are entirely out of service. For instance, as long as Australia kept the FB-111 in service you would find rows of FB-111s here at the AMARG. But, now that Australia has stopped using the airplane, those airplanes are gone. The burden of paying for the storage (as well as parts inventory and disassembly) is on the operators of the airplanes.
It's probably going to be warm; best to get here early.
In any event, you'll want to arrive when the doors first open to catch one of the fifty seats on the bus for the first AMARG tour of the day.
The tour of the facility is entirely by bus. There's a short stop at the entrance to the base where all the passengers must wait in a sheltered garage while your belongings (which you leave on the bus) are searched. Our volunteer guide was quite good (she knows her airplanes)--as I'm guessing they all are.
There are different categories of storage. Some airplanes could be flying in just a few days, while others are only waiting to be disassembled and scrapped.
In some cases a single example of a particularly model has been kept for display.
Back to the museum...
There are a few enclosed (and generally cool) hangars, but many of the airplanes on display are outside. The museum has grown and expanded several times since it first opened, so I would expect that in the next several years, there will be more hangars and more airplanes brought indoors.
Expect to spend the entire day.