Disease was certainly a problem, especially for Native Americans who didn't have the same heritable immunities as people of European descent. But the violence of the American West has been dramatized quite a lot.

You're statistically more likely to be shot Chicago today than you were to get shot in a place like Abeline.

Now, there were certainly incidents of violence. In the Coffeyville raid, for example, the Dalton Gang attempted to rob two Kansas banks but were cut down by armed citizens. Many people, especially ranchers and property owners, kept guns, although six-shooters were rarer than you might think. Shotguns ard rifles were more accurate and more practical for hunting and self-defense. Or the Lincoln County War, the basis for the (heavily dramatized) film Young Guns and one of several grazing disputes that turned violent during the period.

But all the same dime novelists and cowboy films have made the "Wild" West to be a good deal more violent than it really was. Shootouts make for good drama, but they were something of a rarity.

Like others have said, disease was common, as was drought, and also failed homesteading.

However, when you think about duels, cowboys, and saloon doors, that's all a fiction. Cowboys were more like what we now think of as ranchers.

The misconceptions come from western fiction of the time. Pulp novels that romanticized the west were sold to people in the more populated east, which was escapism from the urban population crisis' of the industrial revolution. They were pretty formulaic with very common themes, which evolved into our conceptions of the west. The genre really took off at the turn of the century, when the west was becoming less of a frontier, and people were nostalgic. That's when you see the popularity of "Wild West Shows" skyrocket, which also strengthened these misconceptions.

Source: "History of the West Through Film," taken at the UofO in 2005 (I think) taught by Professor Ostler.