Sure, it was called Daisy Hill Puppy Farm, but even such a pastoral-sounding name isn't really all that great once you think about it. Where do puppies come from? The puppy farm. It's suspect to me, especially with the apparent prevalence of Amish puppy mills, ostensibly on their farms.
Snoopy lucked out, really. Charlie Brown clearly loved him, his dog house was apparently totally sweet (many strips refer to billiards rooms and such), he had his own typewriter, and a very rich imagination. Really, if you think about Snoopy's behavior in the context of a real Beagle that you might keep as a pet, he was kind of a, well, freak. I know he's an anthropomorphized comic strip Beagle, but really, he was sometimes paranoid and erratic, and unpredictable. Not qualities you really look for in Man's Best Friend, especially in the context of the 42 pointy teeth they keep in their mouths (best case scenario, anyway; puppy mill dogs are not known for their exemplary dentition).
So, why did Charles Schultz write Snoopy in quite this way? Especially, as The Examiner article I linked above describes, with him having been given up once (his owner moved to an apartment) and trying to visit the Daisy Hill Puppy Farm where he came from and finding only a parking lot. Was this some of Schultz's dark humor, where the Farm was shut down for being a mill? Were things like that even considered "bad" when Schultz was writing? Was it really just the normal Peanuts bittersweetness, and I'm reading too much into it? I don't really know. I know it's like the reason that Family Guy had an episode where Brian discovered that he was from a puppy mill, though we typically can't look to cartoons to be historically accurate.
Really, when we expand, where did Lady from Lady and the Tramp come from, other than being what might have been a bad surprise Christmas present? And what did Lady and the Tramp's owners do at the end, with their mutt (I mean "designer breed") puppies? Of course, this isn't an example of puppy milling, but rather what might be called "backyard breeding", but also, Lady and the Tramp were in love, weren't they?
(a quick Google search tells me that 1. Tramp was apparently a "Schnauzer mix" and 2. A Cocker Spaniel + a Schnauzer = Schnockers. I am so freaked out by this.)