Bill Ersthaler, back row, second from left, and the rest of his crew training at Davis-Monthan Field in Tucson in the fall of 1944.
On, I dunno. I can think of a two-word answer that might have had a bigger impact on Tucson than a mere war: air conditioning. Prior to widespread a/c, much of the South and Southwest was nearly uninhabitable, at least for commercial purposes. Population of Pima County, Arizona, in 1940: about 73,000. Now: about 975,000.
Fantastic photo
What turned Tuscon into a liberal bastion?
World War II changed Tucson more than any other event except for one--the Gadsden Purchase.