Interestingly enough, that was part of the 'wildness' of the wild west. Obviously it was still far more sexist and racist today, but many African-Americans went west in the hopes of escaping the prejudice they experienced in the South, with nearly a fourth of 'cowboys' (in the literal, ranching sense) being Black. Manpower was short enough that traditional society couldn't really 'stop' a woman from doing much of anything - women ended up running bars, running protection on coaches, ranching, etc.