Marcus is President of M. R. Letourneau and Associates Inc., a specialized heritage and strategic planning firm focused on creative solutions for the management of cultural heritage resources. He is also an Adjunct Assistant Professor in the School of Planning and Contributing Associate for the Heritage Resources Centre at the University of Waterloo and an Instructor for the Cultural Resource Management program at the University of Victoria and at the Willowbank School of Restoration Arts. He co-teaches the facilities management course for the Ontario Museum Association. As of September 2023, he serves as a Subject Matter Expert/Course Author for Algonquin College’s new Bachelor of Applied Science in Building Conservation (launching 2025). He currently serves on the Board of Directors of ICOMOS Canada, the Kingston Frontenac Public Library, and as Chair of the Leeds and Thousand Islands MHC and the interim Canadian Committee of Blue Shield International. He co-authored the second edition of Heritage Planning (Routledge) with Dr. Hal Kalman (2020).