Mrvan worked in industry and banking. He worked for the Mobil Oil Company, where he was a union member. He became a Cost Accountant for M and T Chemical Company, and Bank Financial Officer for National City Indiana. Mrvan entered politics, joining the
Democratic Party, which became a force in the region by the 1930s. He was elected to the
Indiana Senate in 1978, and, with repeated re-elections, served from 1979 through 1995. Mrvan was elected again in 1998. Redistricting passed by the Indiana General Assembly in 2011 shifted the State Senate 1st district's boundaries, effective January 2013. The district was changed to include Hammond's 4th, 5th, 6th city districts, the town of
Munster, the town of
Highland, the west side of the town of
Griffith, the north side of the town of
Dyer, parts of the town of
Schererville, and part of the City of
Crown Point. ==Personal life==