Arguably (?) the greatest comic strip there is, Peanuts is of course the story of Charlie Brown, his dog Snoopy, and their many friends. Peanuts ran from '50 to '00, with 17,897 strips in total, all of them written and illustrated by Charles M. Schulz. In an issue of The Comics Journal, cartoonist Tom Batiuk wrote that "just beneath the cheerful surface were vulnerabilities and anxieties that we all experienced, but were reluctant to acknowledge. By sharing those feelings with us, Schulz showed us a vital aspect of our common humanity, which is, it seems to me, the ultimate goal of great art." Fantagraphics is in the midst of releasing beautiful volumes of the entire run, that will total 25 volumes once complete. Additionally, most of the comics are available legally online at GoComics.
What to read next if you love it: Pogo, by Walt Kelly