Marshall has represented the North Slope Historic District on the Landmarks Preservation Commission since 2011. He has been a member of Historic Tacoma since 2007 and of the Tacoma Historical Society since 2002. In 2006 and again in 2009, he was awarded an Outstanding Achievement in Historic Preservation citation by Tacoma’s Landmark Preservation Commission. He has been involved in numerous civic causes. Marshall lives with his husband, Geoff Corso, in the Henry and Birdella Rhodes House, a 1901 shingle-style house designed Ambrose Russell in the North Slope Historic District.