The Prints & Photographs Online Catalog provides a few different ways to search collections featuring postcards.

A few tips and tricks when searching can be found below:

• Use both forms of "post card" and "postcard" when searching. Be advised, photographs in the Historic American Buildings Survey Collection include postcards, typically of exterior and interior views. To return results without these, use "NOT HABS" in your search string.
• Browse using postcard format links, found on the left-hand side of the Prints & Photographs Online Catalog. There are numerous postcard format listings, subdivided by years, sizes, and locations.
• Over 500 LOTs (groups of images) contain postcards. You can view LOT descriptions and possibly additional images when selecting "Item from this group", underneath the thumbnail image.
• Larger postcard groups may have container lists that tell how the group is organized and these can be requested in the Prints & Photographs Reading Room. 
• Some groups of images require arrangements in advance to view the materials. If a description of a group includes an "Access Advisory," follow the instructions and links to submit a request.