In 1904 John McCormick sold his river bottom ranch at the confluence of the Blackfoot and Clark Fork Rivers to a land company owned by Montana’s U.S Senator, William A. Clark.  At the confluence of the two rivers, Clark saw an opportunity to dam the flow and create electricity for local mills and the bustling neighbor downstream, the city of Missoula.

W.A. Clark’s engineers from Butte originally showed two locations for the dam.  In September 1905, A. H. Wethey, a partner in the Western Lumber Company, secured water rights for the dam--12,000 cubic feet on the Big Blackfoot in December 1904 and 24,000 cubic feet on the Missoula River.  Some of the land for the dam came from the Bandmann Ranch.

Construction of the Milltown Dam. Construction of the dam on the Missoula River began Friday, September 13, 1905.  Clark apparently stopped construction in November with thoughts of expanding the dam, but it was resumed the next year as before.  Completion of the dam occurred near the end of 1907, and the gates of the dam were closed for the first time on January 5, 1908.  The Missoulian noted that the backwater extended up the Blackfoot covering the old county road to a depth of 12 feet in one spot.  This may have been an effort on Clark's part to cause damage to the Bonner dam upstream, which was owned by his rival.

A party of dignitaries including A.H. Wethey representing Clark’s interests, arrived at the power house on January 9, 1908, to see the lights turned on for the first time.  Clark apparently did not attend this memorable occasion, but Wethey was impressed, saying, "It has been a tremendous undertaking and the work has continued with slight interruptions for the past two and a half years.  The cost of the plant complete will aggregate $400,000…Electricity is a wonderful thing and wherever power plants are introduced there seems to be no limit to the wonderful possibilities that can be accompanied with this great power."

As reported by Dam Superintendent George Slack, materials used in the dam construction included 2 million feet of timber, 5000 barrels of cement, thousands of tons of granite, hundreds of tons of structural steel, 125 acres of land cleared of timber and stumpage, over 600 acres of former agricultural land flooded, and 50 workers on the payroll.

Slack noted that an outlet on the opposite side of the spillway would carry irrigation water to the Bandmann Ranch (Bandmann had sold Clark some of the land needed for the dam), and a fish ladder would be constructed near that outlet.  He added, "…when the last piece of timber is added to the dam it will be in such condition that the highest waters known in this vicinity will not affect it in the least."  His statement was proven wrong by the flood waters that same year, in June 1908.

The dam, not of unusual design, was a timber-crib, rock-filled, 40-foot dam 219 feet long.  The sluice gate section, about 52 feet, was also timber-crib originally, but was later replaced by concrete.  The power house was brick and reinforced concrete with 18-inch walls.  A suspension bridge spans the spillway.  The powerhouse contained five General Electric alternating generators and two General Electric  direct current exciters, two of which still had their original Woodward governors in 2008. The generators were powered by Leffel twin turbines.  At peak generation, the dam was capable of supplying 3,400 kilowatts of power.  It was known as a ”run of the river” dam; the amount of power it can produce is determined by the amount of water flowing in the river.  It also has no flood control, an issue that would soon come to haunt it.  The interior workings of the dam changed little after it was constructed in 1908.

After it was built, the dam employed only a few people, compared to the hundreds of men employed by the lumber mill.  There were four houses on the dam's property for the employees.  Today, only the garages of two remain.  Interestingly Clark employed no outside workers in designing and constructing the dam; he brought them all from other Butte operations.

Originally the power produced by the dam was used by the Western Lumber Mill; the communities of Bonner, Milltown, and Missoula; the street car; and even some areas in the Bitterroot Valley. The dam operator would direct current by means of switches located on the second floor of the power house.  By 2008, the switches were gone, and the power fed into the grid, controlled from Butte.

Over the years there were some changes and updating of the operations at the dam including the concrete sluice gates, and additional turbines. The dam itself was owned by a variety of Clark businesses, all with interlocking directorates. After Clark's death, Montana Power acquired the dam from his heirs in 1929.  In the Story of Montana Power, a blurb for the year 1929 notes only that, "The Company acquired by purchase the small hydroelectric station on the Missoula River and the distribution system in Missoula and the Bitterroot Valley."

Montana Power Company (MPC) had been created in 1912 with the merger of four electric companies.  John D. Ryan, who happened to also be president of Amalgamated Copper and later ACM, was largely responsible for the merger.  With Clark’s dam, MPC owned all the existing hydroelectric stations in Montana.  Ryan remained president of MPC until his  death in 1933.