Which labor union limited membership to skilled craftspeople and focused on economic reforms?

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".

which time period is this? or is this story fictional, i'm going to need more info to answer this question