From 1975 to 2005, Marshall worked freelance for local and national labor and trade magazines and created some of his most compelling work that pays homage to Detroit’s labor force with portraits and candid imagery of workers shot alongside the assembly lines and machinery in factories, shops and plants throughout the metro Detroit region as well as in Dearborn’s Ford River Rouge plant, southwest Detroit’s Zug Island, Flint’s General Motors’ plants and in other areas found nearby in the Midwest’s Rust Belt.
In post-1980 photographs, Marshall captured the city's monumental architecture, industrial environments and life on and off the assembly lines. Stopping in Eastern Market, he caught up with the city’s butchers and locals. And in 1987 he returns to the MCS to photograph it one last time before its final closure 1989. A music lover, Marshall documented nearly two decades of Detroit’s thriving music scene with photographs capturing musicians and performances known to jazz and blues scene at the city’s legendary music venues, including Baker’s Keyboard Lounge, the Detroit Press Club as well as at its legendary music festivals on the city’s riverfront and elsewhere in the city from 1977 to 1993.
