The property of the Empire Copper Company, the largest producer of copper in the state of Idaho, is located on a steep mountain side 3 1/2 miles southwest of the city of Mackay in Custer County. At the height of its production it consisted of 38 mining claims, a smelter capable of handling over 500 tons of ore daily, and a 7 3/4 mile Shay railroad connecting the mines and smelter.

The mine, which was opened about 1884 and worked at various times, was originally organized under the laws of West Virginia as White Knob Mining Co. It was reorganized as White Knob Copper Company on April 24, 1900, under the laws of New Jersey by San Francisco millionaire John W. Mackay and engineer Wayne Darlington, who became president and general manager of the company respectively. They were responsible for a great deal of development work, the construction of a large smelter, and an electric railroad. In 1901 E.J. Mathews succeeded Mackay as president, and in 1902 he was succeeded by Henry J. Luce. Wayne Darlington and his staff resigned in the spring of 1902 after a dispute with Luce and Darlington was replaced by S.F. Boyd, who in turn was replaced by Percy L. Fearn.

In October 1904, after seven different managers had tried unsuccessfully to operate the property at a profit, the company was placed in the hands of a receiver. It was purchased by George W. Young of New York on March 18, 1905, for $1 million. He immediately transferred the property to a New York consortium which, in February 1905, had organized the White Knob Copper and Development Company. William H. Brevoort of New York was brought in as managing director and he requested Frank M. Leland, who was manager of the mining machinery department at the Risdon Iron Works in San Francisco and who also had a reputation of being a practical mining man, to assume the position of general manager. Leland arrived in Mackay in June with instructions to dismantle the plant and wind up the affairs of the company. While looking around the property he found several thousand tons of low grade copper ore which he thought could be successfully smelted. He began selling off surplus machinery, some property the company owned in Mackay, and arranged for leasers to do the mining. In late June he started the smelter and eventually shipped twenty five car loads of high-grade gold and silver bearing copper matte before shutting down the smelter in the late fall. After convincing the owners that the mine could be operated at a profit he began ordering new machinery and also replaced the expensive electric railroad with a Shay locomotive.

On October 17, 1905, Ravenel Macbeth leased the entire White Knob property and in 1906 and 1907 the mine was known as Macbeth Lease.

Organized under the laws of Maine on May 29, 1907, the Empire Copper Company, Ramsey S. Bogy principal financier, purchased the property of the Macbeth Lease and the White Knob Copper and Development Company for one million dollars. Frank Leland was named president and general manager of the new company, and the New York firm of Hobbs and Seeley was engaged to act as brokers for the Empire's stock. But in October the price of copper fell so low that Leland was forced to shut down the mine and Hobbs and Seeley offered to repurchase the stock it had sold. The mine remained idle in 1908 and 1909; the only ore shipped was that taken out on assessment work. During this time Leland left Mackay for California where he salvaged the Balaklala mine, another mine owned by William Brevoort, and also purchased a mine of his own in French Gulch, California. Acting manager at the Empire, John J. Fitzpatrick, kept Leland informed of conditions in Mackay while Leland traveled extensively in California and Nevada. In December 1909 Leland resigned as general manager of the Empire Copper Company, but remained as its president and was always available for consultation with the new general manager Ralph Osborn, who had been working with Leland in Mackay since 1905. In 1910 and 1911 the mine was again operated on the leasing system.

In 1912, after serving two years as general manager of the Waldo Consolidated Gold Mining Company in Josephine County, Oregon, Leland rejoined the Empire as general manager. The mine began shipping its ore to the Garfield, Utah, smelter where John J. Fitzpatrick kept an eye on the weighing and sampling, and sent frequent reports back to Mackay. Copper prices remained high, and in June 1913 the Empire Copper Company declared its first dividend.

In June 1915 a wealthy Ogden business man, L.R. Eccles, and his associates purchased the Empire Copper Company, but made no immediate changes in the management; they also continued the leasing system. The year 1915 was also the most prosperous one for the mine, June shipments broke all previous records.

In mid 1916 the management of the Empire changed. L.R. Eccles replaced Leland as president and Joseph Eccles replaced Ralph Osborn as vice-president. By the end of the year both Leland and Osborn had resigned from the company.

Frank M. Leland, who spent ten years developing the mine from a failure into the largest, most successful copper mine in Idaho, was the only long term manager the mine had. After he left the company they again had a succession of short term managers.

A three mile aerial tramway to replace the 7 1/2 mile Shay railroad was constructed in 1917 and 1918 at a cost of $125,000. Labor problems caused a reduction in ore output, and by 1919 the mine was operating exclusively on the leasing system.

In April 1920 the bookkeeper was arrested for embezzlement, and in January 1921 the general manager, Morton Webber, was apprehended on the same charge. With these financial losses, coupled with the low price of copper, the Empire was unable to pay its bills. In July 1921 the company was placed in the hands of a receiver, and on August 5 the mine was totally shut down.

Eccles and his Utah associates reincorporated the company under Idaho laws on October 8, 1921, renaming it Idaho Metals Company. The mine was operated exclusively by leasers until 1927. This system did not permit the necessary development of the Cossack Tunnel and in early 1928 the company was again placed in the hands of a receiver.

The holdings of the Idaho Metals Company passed out of the hands of the receivers in late May 1928 when the property was purchased by A.J. Anderson and W.E. Narkaus of Victoria, B.C., who immediately sold it to the newly formed Mackay Metals, Chase A. Clark, president. The mine and mill plants were entirely rebuilt, the mine rehabilitated, and an active development campaign started which resulted in the discovery of a large tonnage of new ore in the Cossack tunnel. Lack of money again plagued this new organization and the company suspended operations in August of 1930. Although the leasers continued to work, they stored all their ore. In 1931 the property was sold to the county for taxes.

Although the company remained in receivership until 1939, some leasers worked on the property. In 1937 G.M. Tomle of San Francisco held an option on the property with the Custer County Commissioners, but lack of funds prevented him from doing any work.

Organized by a group of Mackay businessmen for the purpose of operating the old Mackay Metals property, the Mackay Exploration Company acquired the property from the county commissioners in May 1939 and by December twenty sets of leasers were at work; the mine was rehabilitated and reopened to the 1000 foot level, the Cossack Tunnel, at the 1600 foot level, was also reopened and development started. In April 1944 work began under an RFC loan for $45,000 in rehabilitating the mill and power plant for the purpose of conditioning mill and mine for production of 100 tons of ore daily. W.P. Barton became manager of the Mackay Exploration Company in 1945 and a year later he reorganized the company into the Custer Copper Corporation. The mine continued operating under this name until 1950 when it reverted to its former name of Mackay Exploration Company. The mine was idle except for sampling until 1960 when it became the property of R.V. Lloyd and Company, a partnership of R.V. and H.U. Lloyd. The Idaho Inspector of Mines annual report lists the property under this name from 1960 to 1965. In 1968 the report again lists the property under the Mackay Exploration Co., but as an inactive mine. In 1971 the Mackay Exploration Co. was on the inspector's forfeiture list and the Empire group of mines is listed under Lost River Mines, Inc. From 1972 until the inspector's final annual report in 1974 the Empire mines are listed under Honolulu Copper Co., leased to Ivie Mining Company.

Due to the discontinuation of the Inspector of Mines annual report in 1974 further information on the company is not available.