The Mogensen Collection is organized in four series: Personal Papers, Professional Papers, Office Records, and Project Records. The Personal Papers are comprised of biographical material and correspondence. Professional Papers include Awards and licenses, and his involvement with the San Mateo Historical Sites Committee. The Office Records document administrative operations, public relations, and correspondence. Also included are clippings from newspapers and tear sheets from magazines in which Mogensen’s projects were featured.

The Projects Records document Mogensen's projects and designs (1955-1988) through drawings, photographs, and project files. Major Projects include: the Hillside Commercial Center and the Hillside housing development for the David D. Bohannon Organization and Foster City Townhouses. At the end of this series there are a few folders of Cecilia Mogenson’s landscape projects.