Duels did happen from time to time in the 19th century. For example, California Senator David Broderick in 1859 became the only US Senator to die in a duel, and there's a difficult to validate tale of two French men in 1808 holding a gun duel in hot air balloons!

Actually I have a history book about the history of ballooning called Aeronauts that I found at a thrift store. If I remember I'll see what that has to say about this tale because it does call out other largely fabricated tales as such

But like most fictions, the fiction of Wild West duels contains some kernels of truth and certainly makes for great drama