In September 1884 the Montana Improvement Company announced plans to build a 200-foot dam on the Big Blackfoot River, as it was known, to hold logs that would be cut from lands up the Blackfoot. First they would collect a supply of logs in the river and then build a mill (or a series of mills from there to Missoula). Missoulians were excited at the prospect of economic boom for their community.
The dam was constructed by another of Hammond’s relatives, his maternal uncle, Walter Coombes. The initial dam structure did not survive the spring floods of 1885, but it was rebuilt in time for the opening of the mill in 1886. In the spring of 1886, it held 20,000 board feet of lumber behind it. A steam-powered generator and a water powered turbine generated electricity for the mill itself. Power generation was limited to the mill lights. Missoula interests were soon to eye the potential the water power at the dam offered for their growing electric needs.
The first electric plant in Missoula was built in 1889 by A. B. Hammond for the Missoula Mercantile and First National Bank, both of which he owned, as well as the Florence Hotel. In 1890 H.M. Ogden produced 220 volts to power his flour mill at the north end of the Higgins Avenue Bridge. Within a couple of years another enterprise built a steam plant on the adjacent island in the Clark Fork, bringing lights to theaters, saloons, and stores on Higgins Avenue.
In 1895, ownership of generating facilities passed from still another owner, Northwest General Electric, to Hammond's newly incorporated company, Missoula Light and Power (ML&P). Hammond then proceeded to merge this company with the existing water service. In 1898, after obtaining an acre of land from the Big Blackfoot Milling Company for $1, ML&P constructed a powerhouse adjacent to the Bonner mill. This electric generating station sent 3,400 volts to Missoula, replacing the previous generation facility on the island in Missoula.
After Clark's Dam was completed in 1908, the Bonner Dam’s power component was no longer used to supply electricity to Missoula. Clark’s Dam produced much more electricity, and at full pool the new dam just about inundated the older dam. This is clearly shown in Clark’s engineering drawings. Clark purchased Hammond’s Missoula Light and Power in 1906, so he owned both facilities by the time the dam was in operation.
The Bonner Dam was removed in 2007 as part of the Federal Superfund cleanup of the Milltown Dam site.