Clarence Arthur Perry, Cornell University Class of 1899, was employed by the Division of Recreation of the Russell Sage Foundation from 1909 to 1937, when that department closed. He lived in Forest Hills Gardens, a residential unit planned by the Sage Foundation. In January 1924 he devised his Neighborhood Unit theory defining a neighborhood as the area served by an elementary school and bounded by arterial roads; this theory was published in study number 7 of the Regional Plan of New York and Its Environs. Perry also wrote REBUILDING OF BLIGHTED AREAS (1933); PLANNING IMPROVEMENT OF YOUR OWN NEIGHBORHOOD (1935); and HOUSING FOR THE MACHINE AGE (1939). He lectured on his planning theories at New York University, Harvard University, and to various other groups.