You'll have to re-check your info, Sarah, since that which you posted has an obvious error in it.
42nd (Infantry) Division did not have a "1st Regt." (1st Regiment). The three rifle regiments in 42nd ID were the 222nd Infantry, 232nd Infantry, and 242nd Infantry. Each of them would have had a 1st Battalion, and each 1st Battalion would have had a Company B.
For starters, here are a couple of web pages that should be of interest to you: