I was wrong.
In the second store we entered I immediately came across a pack of postcards that drew my interest and made my heart pump fast. In the middle of Kansas, I had just discovered a bundle of San Francisco postcards from around the 1940's (my guess based on the cars in the photos). Unused and still in relatively good condition, I gladly gave the merchant $16.50 for them and mentally figured out just the spot for them in my already stuffed suitcase.
Some of them are posted below: