In order to regulate and restrict the height, number of stories and size of buildings and other structures, the percentage of lot that may be occupied, the size of yards, courts and other open spaces, the density of population, and the location and use of the buildings, structures and lands for trade, industry, residence or other purposes, the city is divided into districts of which there shall be four in number known as:
A. "A" Single-family dwelling district;
B. "B" Multiple dwelling district;
C. "C" Commercial district;
D. "D" Industrial district (Prior code § 11-2-1)