In order to classify, regulate and restrict the locations of trades, industries and the location of structures designed for specified uses, to regulate and limit the height and bulk of structures hereafter erected or structurally altered, to regulate and limit the intensity of the use of the lot areas and to regulate and determine the areas of yards, and other open spaces within and surrounding such structures, the City is hereby divided into the following use districts:
(a) OS Open Space District
(b) R-1 Single-Family Residential District
(c) R-2 Single-Family Residential District
(d) R-2A Single-Family Residential District
(e) R-3 Two-Family Residential District
(f) R-4 Multiple-Family Residential District
(g) C-1 Neighborhood Commercial District
(h) C-2 General Commercial District
(i) C-3 Uptown Commercial District
(j) C-4 Office, Laboratory and Research District
(k) C-M Commercial-Industrial District
(l) M -1 Controlled Industrial District
(m) M -2 Industrial District