Project Files span the period 1958 to 1998 and document projects ranging from private residences and residential developments to institutions, such as the San Francisco Ballet Association Building; and urban development projects, most notably the Yerba Buena Gardens project in downtown San Francisco. Also included are records and design documents for Aliamanu Valley New Town, a military base in Hawaii that was the first major project designed with CARLA, computer software for architectural design created by Willis, and sketches of unbuilt structures designed for writer Alex Haley.

The series is comprised of presentation drawings, slope analysis drawings, site plans, maps, cut-and-fill analysis plans, sketches, conceptual design drawings, construction drawings, as well as correspondence, research files, contracts, environmental impact statements and studies, financial records, and feasibility studies. There are records for more than 150 projects. Drawings are large folio, pen-and-ink or watercolor on paper, linen, or mylar. Some are heightened with color.