The Blue Hole
The Blue Hole is a freshwater pond that was a tourist site from the 1920s to 1990, with 165,000 visitors annually.

The Crystal Cave
The limestone Crystal Cave was discovered in 1897 and can still be visited today.

The Erie, Pa. Series
Postcard series by Harry H. Hamm

Let’s Explore Ohio
“Let’s Explore Ohio” free scenic postcards were available only through Standard Oil stations and dealers.

Meiler Series
Series of C.T. American Art postcards from the 1920s

Ohio University
Postcards featuring Ohio University in Athens, Ohio

William McKinley Monument
Postcards featuring the Wm. McKinley Monument in Canton, Ohio