Little Nemo in Slumberland: 22 July 1906. Little Nemo In Slumberland was artist Winsor McCay’s masterpriece: weekly strips of a gigantic size, chronicling the fantastic dreams of a boy. You can find some digital copies at the Digital Comic Museum, a free and legal sharing service for public domain golden age comics. Check them out.
Little Nemo has been collected a few times. I like the “So Many Splendid Sundays” Vol. 1 & 2 because they are printed on large pages like the originals. But if you are looking for a complete collection, you want either the six-volume set published by Fantagraphics, or the two-volume hardcover collections by Checker.