Well, you can buy used copies of the U.S. Acres strip collections on Amazon.com, but you can also check out many strips on this page.
[link] Incidentally, there's a bunch of differences between the strip and the animated series it spawned; Orson's rotten brothers weren't originally named, Bo's an idiot, Sheldon has a philosophical side, and there's a cat and a dog who never appeared in the animated version (most likely because the show already had Garfield and Odie).