What posed the greatest challenge to pioneers crossing the western mountains?

in 1897, pershing became a tactical officer at west point, and that's where he was given the nickname "black jack." pershing's first name is "john," for which "jack" is a nickname, and he was a white man who commanded black troops. hence "black jack".

1 > george s. boutwell

2 > general ulysses s. grant

3 > james a. garfeild

4 > adolph e. borie