The principal American firms interested in the development of the Canadian chromite deposits during the past few years have been the Mutual Chemical Co., the Harbison-Walker Refractories Co., the Electrometallurgical Co., and the Quebec Asbestos & Chrome Co. The last-named company purchased one of the concentrators built by the Mutual Chemical Co., and has furnished a considerable output both of crude ore and concentrates. Canadian firms have also produced considerable ore. With the close of the war and the drop in the price of chromite, the Canadian mines have been largely abandoned. It is possible, however, that some American firms that mine ore for use in their own plants may continue work on a small scale. When the _United States_ was the world’s principal chromite-producing country, the output came from the eastern United States and principally from Maryland. The Wood chrome mine and neighboring deposits in Baltimore and Harford counties furnished most of the production. Smaller amounts were mined in North Carolina and Pennsylvania. The principal chromite deposits of the United States, and those that have furnished nearly all the ore produced in recent years, are in California and Oregon. Recently deposits of some extent have been found in Montana, but these have not reached the producing stage. The chromite deposits of California are for the most part grouped into four principal districts, the Klamath Mountains region of northwestern California and southwestern Oregon; the Coast Range of west central California; the Sierra Nevada range throughout a considerable part of its length; and the San Luis Obispo district of southwestern California. The chrome ores of California and Oregon form lenses or irregular bodies in serpentine and related rocks. Many of the ore bodies are found in comparatively fresh peridotite and dunite, and the intimate relation between the chromite and the associated pyroxene or olivine is well shown. In places, also, chromite masses are found in the mantle of residual material derived from the alteration of serpentine and other rocks. Most of the chrome ores of the Pacific Coast are of low-grade, few running more than 45 per cent. chromic oxide. Concentrating plants have been built to beneficiate the ore from bodies large enough to warrant such expenditure. At some plants the grade of ore was thus raised to more than 52 per cent. Locally small bodies of high-grade ore have been found.