Milwaukee, Wisconsin, was a magnet for immigrants throughout the 19th century. The largest group came from Germany, beginning in the 1840s. The next-largest group came from Poland in the decades after the American Civil War. Other large groups included British, Irish, Scandinavians, Serbians, and Russian Jews.
The bride in the portrait above looks Southern or Eastern European to me. Does her dress give you any clues about her cultural background?
The portrait was made at the studio of William Wollensak. The design on the back of the cabinet card is particularly elaborate and artistic.