Although the museum was conceived as a small memorial institution, it almost immediately became a collecting museum, and the space afforded by the existing facility quickly became inadequate. In 1964, three years after the museum first opened, a 14,250-square-foot addition was completed on the west side of the original building to provide room for offices, a bookstore, a research library, and an art-storage vault. Joseph R. Pelich (1894–1968) of Fort Worth, an associate architect of the original building, carried out the work after Philip Johnson expressed little interest in taking on the project.