The publication of the first volume of the Complete Peanuts raises the question that Peanuts fans love to debate into the small hours -- or would, if we Peanuts fans weren't too square to stay up that late -- when did the strip hit its peak, and when did it pass its prime? (I'd prefer not to say "jump the shark" unless it's completely unavoidable.)
Some have argued that Peanuts jumped the shark (there, I said it) when Snoopy displaced Charlie Brown as the primary focus of the strip. This was the theme of a widely-discussed article called Against Snoopy. It's a good article, and a plausible argument, because it's quite true that by the time the strip ended, Snoopy had taken over the strip to an unhealthy extent, supplanting Charlie Brown's trademark bittersweet humour with more upbeat, fanciful material. The problem with the argument is that when the strip was at its peak, Snoopy was not the one-dimensionally happy character that the author seems to think he was. Snoopy's humor derived in part from his frustration at being just a dog ("If I were a human, I wouldn't even own a dog!"). He represented the alternative approach to Charlie Brown: Charlie Brown hates his life so he gets depressed, while Snoopy, who hates his life just as much, creates alternative fantasy lives for himself. In that sense, they are the two sides of Charles Schulz: the depressed moper and the creative artist. Both depression and creativity are responses to the same feeling of dissatisfaction with one's life.
I would say that Peanuts' peak period began in the late '50s, when Schulz started doing continuing stories in addition to daily-gag strips. (The early strips are almost entirely self-contained gags.) Doing stories about Charlie Brown's agonizing failures, or Snoopy's fantasies, or Linus and his teacher Miss Othmar (like the story where Linus assisted Miss Othmar during a teachers' strike and inadvertently caused her to get fired), helped to establish those characters more firmly and expand what we knew about them. The strip pretty much went from strength to strength for years after that.
The first "shark jump," in my opinion, occurred when Woodstock got his name. This happened late in 1970, the year which is currently being reprinted at the Peanuts Website, so they should be getting to it soon. Before that, Snoopy was mostly just irritated by Woodstock, calling him "that stupid bird" and sitting by while Woodstock did something stupid. After the bird got his name, Snoopy and Woodstock were suddenly best friends, and while their relationship produced some nice moments, it also produced some cutesy-poo and sentimental moments, and took up a lot of time; even Schulz said in 1971 or 1972 that he'd gotten complaints that Snoopy and Woodstock (whose strips often appealed mostly to the strip's younger readers) appeared too much. It also took the edge off Snoopy's character. It used to be clear that he fantasized as a way of escaping from a life he doesn't much like; after he obtained a permanent "best friend," he was just too happy-go-lucky, and he and Woodstock started eating up too much of the time in the strip, which left less time for the characters of Charlie Brown or Linus to be developed.
And come to think of it, the introduction of Marcie in 1971 or so may have been a similar problem -- i.e., giving Peppermint Patty a permanent sidekick took the edge off *her* character, since she was originally defined as being lonely.
By the mid-'70s, while Schulz's extended stories were as good as ever and perhaps better than ever (Peppermint Patty's skating odyssey, Charlie Brown and the EPA, Linus on the barn roof), the daily gags had gotten sillier and less philosophical than before, so you sometimes have to sit through a lot of "Woodstock does something cute" gags in order to get to the next story. Also, all the attention paid to Peppermint Patty and Marcie, while often entertaining, helped take the focus even further away from Charlie Brown.
In the end, I'd pinpoint the end of the peak period around 1975, with:
a) The introduction of Spike and other Snoopy relatives b) A slight change in format, with thinner panels and thus less room for interesting visuals, and c) The Snoopy and Peppermint Patty stories have begun to take up so much time that there's no more room for interesting Charlie Brown stories like the Mr. Sack series (from 1973).
I don't have much of an ending for this, except to say that:
- There were still worthwhile strips in the last 20 years of the strip; the kids' visit to a fundamentalist summer camp, in 1981, was a classic, and rather gutsy (Peppermint Patty: "Forget it, ma'am -- maybe the world will end tomorrow, but I wasn't born yesterday"), and the last few years of the strip produced some surprisingly fine strips with Linus and Lucy's previously useless little brother Rerun.
- It's amazing that a comic strip could have a "peak" that lasted (at my estimate) something like 20 years. Most strips don't even last 20 years, and those that do usually burn out much earlier than that (Walt Kelly's Pogo was already getting sort of tired by the early '60s; and let's not even talk about how far Calvin and Hobbes had declined into preachiness and self-conscious artiness by the end of its short run).