He served four years on Watertown's Common Council, and four as president of the city fire and police commission, and was mayor of Watertown from 1915 to 1921, a title previously held by his father (Henry Mulberger Sr.) and two of his brothers, Henry Jr. and Arthur (whom he succeeded).

In 1914, Mulberger was elected to the Wisconsin State Senate from Wisconsin's 33rd State Senate district (Jefferson and Waukesha counties) as a Democrat, with 5,890 votes, to 5,157 for Republican Frank Foote, 61 for Prohibitionist J.

[2] He gained statewide attention as the author of the 1919 "Mulberger Act", which provided for enforcement of the Prohibition Amendment, but legalized the sale of near beer with up to 2.75% alcohol content (the latter provision was eventually defeated in court).

[4] Mulberger ran once more for mayor of Watertown, but came in third in a tight three-way race, with 1271 votes to 1461 for J. E. McAdams and 1406 for A. H.

[5] In 1928, he was the Democratic nominee for Wisconsin Secretary of State, losing to incumbent Republican Theodore Dammann, who drew 627,244 votes to 232,797 for Mulberger, 36,734 for Socialist Leo Krzycki, 6,517 for Prohibitionist W. C. Pickering, and 1,510 for Peter Ordanoff of the Workers' Party.