Outcault! Opper! Great stuff! I'd love to get a copy of Pore Lil' Mose, it always seems to go pretty high (even in poor condition), and some people buy the book just to seperate the pages and individually frame them! Great for decorators, but just try to sell an individual page to a collector afterwards... not worth it. For Opper fans, Bill Nye's History of the United States book (329+ pages) is a treasure trove with an approximate average of an illustration every other page or so... here's a sampling:
I'm wondering if he was a direct influence on R. Crumb.
Notice the Alfred E. Neuman looking chap?