Eighty-seven placer districts in Arizona are estimated to have produced a minimum of 564,052 ounces of placer gold from 1774 to 1968. The location, areal extent, past production, mining history, and probable lode source summarized for each district are based on information obtained from a wide variety of published reports relating to placer deposits. Annotated references to all reports that contain information about individual deposits are given for each district. Most of the placer gold found in Arizona was derived from systems of small gold-quartz veinlets and stringers scattered throughout the bedrock of the adjacent mountain ranges. In only a few localities was the gold in large placer deposits derived from well-defined vein systems mined for the lode-gold content. The most productive placer mining era was 1858-80, when rich deposits of placer gold were found in the southwestern and central parts of Arizona and hundreds of individuals worked the rich surface accumulations of gold. Subsequent placer mining was done by individuals working small deposits in many areas of the State using small-scale portable equipment, such as rockers, sluices, and drywashers. Large-scale dredge operations were active in a few districts.