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".
general allotment act (dawes act) february 8, 1887
amendment to the dawes act, february 28, 1891
commission to the five civilized tribes (dawes commission), march 3, 1893