I've talked before about the influence of Westerns on Dungeons & Dragons, so it's really no surprise that one of the earliest RPGs TSR produced after OD&D would be Western -- Boot Hill. Its original incarnation, which I never saw, was published in 1975 and was written by Brian Blume and Gary Gygax. Historically, this is interesting, because it reminds us (once again) that Brian Blume was not just a monied hanger-on but also a game designer in his own right. It's also a rare example of non-D&D work by Gygax, something one didn't see much of.
The edition I owned was the second, pictured here, which was published as a boxed set in 1979. The set contained a 36-page rulebook, a double-sided map, some counters, and old school percentile dice. As you would expect, the rules are very sparse, focusing largely on combat. Indeed, reading Boot Hill, one is immediately struck by how much more combat-focused it is even than D&D. This isn't surprising, since gunfights, saloon brawls, knife throwing, and the like are the primary things the game is intended to simulate. Most other actions could just be improvised either through roleplaying or simple random adjudication. In this respect, Boot Hill is the epitome of "old school."
Much like Dawn Patrol, there's a sense in which Boot Hill is more of a wargame than a RPG. Its concerns, both mechanically and thematically, are centered on violence in all its myriad forms. To call it, as its subtitle does, a "roleplaying game of the Wild West" is to be fairly generous, even in my eccentric opinion. While there are rules for forming posses, aging, and earning a living, they're quite vestigial. Playing a lengthy Boot Hill campaign would take some remarkable creativity on the part of the referee, even moreso than in OD&D, which at least sketches out an endgame. This gives Boot Hill a vaguely "beer and pretzels" sort of feel to it, as if it were intended primarily as a simulation of Wild West shoot 'em ups rather than anything more ambitious.
I know I never managed to do more with the game than run fistfights and showdowns. We had fun with the rules, but I cannot now tell you the name of a single character or recount a single session of our play in any detail beyond a vague recollection of a character getting access to a Gatling gun and laying waste to a lot of desperadoes who were attacking the town. Perhaps that speaks more to our immaturity, I don't know. Being a big fan of Westerns, I've always wanted to run and/or play in a Western RPG campaign, but, if I ever did so, I doubt I'd turn to Boot Hill to do it. Even with my level of simplicity and do-it-yourself elegance, I'd need to create too much from whole cloth. Thus, Boot Hill is an example of an old school game that I think doesn't live up to its full potential -- a pity.