Wendover, Utah (a stock airfield) hosted the 509 Composite Group before it left to drop the Bomb.
Buckley AB in Colorado goes back to WWII and is still and active ANG base.
Washington State has McChord AB, Fairchild AB and Yakima Firing Center (two airstrips).
I also like to use:
Abandoned_B-29_training_fields.zip
Pocatello_2.zip
These two files will give you:
Bruning AB, NE
McCook AB, McCook, NE
Walker AB, Hays, Kansas
Pocatello AB, ID
Most of the available US Navy Naval Air Stations available as addons were active in WWII.