Long before Colorado became a State, the tumultuous progress of hard-rock mining had given rise to milling, smelting, and manufacturing enterprises. An arastra, a primitive ore crusher of Spanish origin, was at work in Gregory Gulch early in the summer of 1859, pulverizing "blossom rock" and other soft ores from decomposed surface veins. The mule-driven arastra soon gave way to stamp mills powered first with water, later with steam. Harnessing small but swift mountain streams, miners built scores of water wheels to turn cam shafts that lifted heavy stamps, huge blocks of iron, with which ore was pounded to dust. As more refractory ores were encountered, such crude methods proved increasingly inefficient, recovering less than half the precious metals contained.

After much experimentation smelting solved the major problems posed by Colorado's peculiarly difficult ores. Nathaniel P. Hill, metallurgist of Brown University, organized the Boston and Colorado Smelter Company and in 1868 erected the State's first smelter at Blackhawk in Gregory Gulch. For several years this plant and the others reduced crushed ores by concentrating gold and silver on a copper matte; these plates were shipped to refineries in Swansea, Wales, and other points abroad. The Boston and Colorado Smelting Company built its own separating works in 1873, and five years later erected its Argo plant in Denver where coal was cheaper. Other notable smelters in Colorado were the Leadville Smelter (1877), the Grant Smelter (1878) in Denver, the Arkansas Valley Smelter (1879) in Leadville, the Durango Smelter (1872), the Globe Smelter (1886) in Denver, and the Philadelphia Smelter (1888) in Pueblo. In 1899 the larger smelting interests in the State were merged as the American Smelting and Refining Company by the Guggenheim brothers, who had founded their family fortune on the mines and smelters of Leadville. As more complex ores were encountered, new processes were introduced to extract the five basic metals—gold, silver, copper, lead, and zinc—and to separate these from one another. In 1896 a chlorination mill had been erected at Cripple Creek to concentrate ores for shipment to the smelters. The cyanide process, however, proved more satisfactory and is still employed by the Golden Cycle Mill at Colorado Springs, the largest in the State. Colorado mining engineers pioneered the introduction of the cyanide process and have invented many important devices for the treatment of low-grade ores.

The most recent development in this field is a process known as selective flotation, by which metals are amalgamated in a froth of crushed ore, water, air, and oil. The amalgamated minerals are then floated off, much as cream from a milk separator. So effective is this new method that each mineral can be floated off separately as a very high concentrate. Tons of tailings from old ore dumps are now being treated by the process.

Much mining machinery to meet local needs has been designed and manufactured in Colorado shops, which early established a reputation that made them centers of such manufacture for the entire Rocky Mountain region. In 1869, Peter McFarlane established at Central City a foundry and machine shop that still manufactures crushing, hoisting, milling, and smelting machinery. The larger machine shops and foundries are now concentrated in Denver; coal mining and beet sugar refining have created new demands for specialized machinery, much of which is manufactured in and around Denver. In 1921 several large manufacturers merged their plants and erected the General Iron Works at Englewood, in Denver's suburban area. The total value of machinery manufactured in 1935 was less than $3,000,000 but has advanced steadily in recent years. Sheet, structural, and ornamental metal works manufactured $2,000,000 of products in 1935, and railroad repair shops almost $5,000,000 of equipment.

The requirements of the machine industry and the growing demand for steel rails, wire fence, and other metal goods, led the Colorado Fuel & Iron Corporation, the largest coal producer in the State, to erect an open-hearth steel plant at Pueblo in 1881 ; today this plant is the largest steel mill west of the Mississippi, with an annual capacity of 600,000 tons; the largest single industrial establishment in the State, it employs 6,000 to 7,000 men.

The Gates Rubber Company in Denver, the largest producer of rubber goods between Akron and the Pacific Coast, employs an average force of 1,500 men in manufacturing products valued at more than $8,000,000 a year. Other Denver manufactures include furniture, wooden and paper boxes, barrels, clay products, and printed material.

As mining stimulated the manufacture of machine and metal products, so the rise of agriculture early in the twentieth century gave rise to complementary industries. Slaughtering and meat packing is one of the oldest enterprises in the State and at the peak of its production in 1919 had a gross income of more than $41,000,000. The meat packing industry, concentrated largely in Denver and Pueblo, with nineteen plants in operation in 1935, employed 1,700 workers in that year; their products were valued at $31,673,264.

The beet sugar industry began with the construction of a refinery at Grand Junction in 1899. In 1901 a second factory was constructed at Loveland, and the success of this venture led to the building of other processing plants. Four companies—the Great Western, Holly, American Crystal, and National Sugar—have eighteen refineries in Colorado; thirteen mills are in the South Platte Valley in the northeastern corner of the State, three in the Arkansas Valley, and two on the Western Slope. Colorado refines more beet sugar than any other State. Other industries complementary to agriculture are flour milling and the bakery business, each of which yielded a gross income of more than $9,000,000 in 1935. Fruit and vegetable canneries, and plants making jellies, sauces, preserves, and salad dressings have been established in all of the chief irrigated areas, having a total gross revenue of $3,680,000 in 1935.

Four industries—steel, sugar, meat packing, and rubber—contributed more than half of the $67,159,613 that Colorado factories added to the value of raw materials in 1935. Of the State's 402,867 gainfully employed workers in 1930, 76,734 were engaged in the manufacturing and mechanical industries, more than four times the number employed in the extraction of minerals but less than three-fourths of those employed in agriculture. The remainder of Colorado's employed find work in the building trades, retail and wholesale commercial enterprises, personal service occupations, and the professions that have grown up around the basic industries of mining, farming, transportation, and manufacturing. In November 1937, according to a Federal survey, 67,708 Coloradoans were unemployed, of whom 23,140 were working on emergency relief projects; at the same time 23,867 were registered as employed only part-time. Subsequent economic recovery has absorbed some of the unemployed, but the number of young employable workers has simultaneously increased.

Colorado's labor legislation compares favorably with that of other States. In June 1887 the legislature established a Bureau of Labor Statistics, charged primarily with enforcing labor legislation; it was also authorized to arbitrate labor disputes and to establish free employment agencies. The bureau continued to function until 1917, but in 1915 many of its functions were transferred to the Colorado Industrial Commission established that year. The commission, its members appointed by the governor for a term of six years, is the agency now charged with the enforcement of the Workmen's Compensation Act, minimum wage laws for women, child labor laws, and similar legislation. The State mining laws, based upon years of heated controversy, are among the best in the Union. The State Unemployment Compensation Act meets the minimum standards established by the Federal Government. In 1911 the employment of children under the age of fourteen was forbidden and the employment of children between the ages of fourteen and sixteen was restricted to months when schools are not in session.

The right of workers to organize in labor unions was recognized by the State in 1897 and elaborated in 1911. The right of collective bargaining was not included in these statutes, however, and in 1939 the legislature defeated a "Little Wagner Act" designed to extend the provisions of the National Labor Relations Act to intra-state industries. Present Colorado statutes outlaw blacklisting and the "yellow dog contract." For many years a State law prohibited the use of the boycott and peaceful picketing in industrial disputes, but in May 1939 this statute was declared unconstitutional by the State Supreme Court. Payment of wages in scrip is forbidden, and employees are forbidden to use false advertising in recruiting strikebreakers. Employees must give thirty days' notice before calling a strike, and employers likewise before declaring a lockout.

All in all, the tangible wealth of Colorado was estimated in 1937 at $3,434,000,000, exclusive of vast known but as yet undeveloped resources that may some day acquire enormous value.