Or by "union worker" did you mean he is employed by the union and visits various states to represent union members in those states?
I know it's irrelevant- the point is he travels state to state frequently. I cannot remember what our CPA used to do if we filed every single state return or just our one we live in.
Is your husband perhaps employed as an OTR truckdriver? If so, Public Law 101-322, Sec. 7(b)(1) provides that, if he has assigned duties in 2 or more states, his pay is subject to state income tax only by his state of residence.