Dr. Marshall McLennan was born on 1932 October 16 in San Francisco, California. He graduated from Menlo School (Atherton, California) in 1950 after attending American High School in Manila (Philippines) for his freshman through junior years. McLennan has lived in Ann Arbor for over forty years, and married Janet Gertrude (Phillips) on 1965 December 18 in Bridgeton, New Jersey. The McLennan's have one child, Lindsey Seaton McLennan. McLennan received an Associate in Arts from Menlo College in 1951, and received his Bachelor of Arts in Political Science from the University of California, Los Angeles (UCLA) in 1955. From 1955 through 1957 McLennan was in the United States Army, attaining the rank of Lieutenant. Between 1957 and 1960 McLennan worked for Dun and Bradstreet in San Francisco, and at Graybar Electric Company (San Francisco, California) from 1960 to 1962. In 1965 McLennan received his Master of Arts in Geography from San Francisco State University, and 1973 he received his Doctor of Philosophy in Geography from the University of California, Berkeley. McLennan was hired to teach in the Geography and Geology Department at Eastern Michigan University (EMU), where he founded the Historic Preservation program (1979), from September 1970 until his retirement in 1999. After his retirement, McLennan returned to EMU to instruct the American Vernacular Architecture course for the Historic Preservation program.

In the mid 1970s, McLennan and EMU colleague, Andrew Nazzaro, developed a historic survey project (requested by the Michigan State Historic Preservation Office) that called for surveying historic sites along the Huron River. The purpose of the survey was to identify important patterning regarding post-contact settlement of Washtenaw County, and the use of water power that helped facilitate subsistence farming. After securing approval for a sabbatical and fiduciary support, McLennan and Nazzaro started working on the survey project and the framework for a historic preservation program. Early on Nazzaro left McLennan for another EMU project in Yemen, and McLennan completed the survey project. The survey project led to a proposal, developed by McLennan, to create a program in historic preservation at the University. The Historic Preservation program was approved in 1979 and had twenty-three students in the inaugural class.

McLennan has been involved with the National Trust for Historic Preservation, Michigan Historic Preservation Network, National Council for Preservation Education (1979 – 1997), American Association of Geographers, American Geographical Society and the Pioneer American Society. McLennan has also served on the Michigan State Review Board, Washtenaw County Historic District Commission, Ann Arbor Landmarks Study Committee, Ann Arbor Individual Historic Properties Study Committee (1992 – 1998) and the Demetrious Ypsilanti Memorial Restoration Study Committee.

McLennan and his wife now reside in New Mexico.