Ooh, gotta disagree with yah there, pardner.
Historical evidence suggests that the fraction of Americans in the "old west" who owned firearms was surprisingly low. Way, way lower than the percentage of citizens owning such weapons nowadays, for example. Guns were quite expensive, particularly compared to the discretionary cash available to the average subsistence farmer or cowboy. Frontier boomtowns tended to go through a brief, chaotic and violent formative stage, generally followed fairly promptly by the imposition of something resembling the rule of law. Vigilantism and frequent gunfire were just plain bad for business.
Then I suspect the historical evidence is wrong, unless by "firearms" you mean handguns. Most of the area west of the Appalachians even after the turn of the 20th century was rural and small town, and few farmers didn't have a gun of some kind, usually a shotgun. They were a tool, though, not usually thought of as a defensive weapon. They were used to kill varmints, stray dogs, to hunt with, and to put down animals that were injured or too old to keep. When I was a small child, in the late 40s, I lived in a farmhouse on the edge of town, and both my house and the house across the way (where I spent a lot of time playing with the neighbor kids) had guns behind the basement door, .a .22 and a pump 12-gauge. I personally own guns from four generations of my ancestors, and not a single one of the hand-me-downs is a handgun or a military weapon -- they're all behind-the-door tools.