The United States Senate Catalogue of Graphic Arts
You can also access it online... but I highly recommend getting your hands on these gorgeous print reproductions.
After finding this randomly in a LexisNexis search, we couldn't locate our print copy in the catalog. Our amazing staff managed to locate it, update our catalog record, and it's sitting on my desk in all its large-format hardback full-color glossy-paged glory. Government + art + history + books... there is nothing I don't love in this equation.
It's got a whole section just on old political cartoons--with one that rings true today, featuring Uncle Sam riding a snail labeled "U.S. Congress." The cartoon is titled "The Lightning Speed of Honesty."
Ah, some things don't change, eh?