The Milwaukee Railroad's "Duck Bridge" from 1979.A third railroad eventually made its way into the small communities of Bonner and Milltown. The Chicago, Milwaukee and St Paul Railroad, also known as the Chicago Milwaukee and Puget Sound Railroad, came through on the south side of the Clark Fork in 1909. A spur from the main line of the Milwaukee, as it came to be known, crossed the river well above the Milltown Dam “reservoir” on a covered bridge.

It was especially significant for the Blackfoot Mill (and later Anaconda) that in 1910 the Milwaukee acquired the Big Blackfoot Railway and ran the spur track to the logging camps near Potomac. This played a vital role in bringing timber from the Blackfoot valley to the mills. The Milwaukee acquired the rights to bring all the logs into the mill, even those that came in on the Northern Pacific from the Thompson Falls area were switched into the mill by the Milwaukee

The main line of the Milwaukee ran through Missoula and on to the west coast. The Anaconda Company encouragement of electrification of the railroad (which would also help distribution of Anaconda’s copper) was no doubt a factor in the decision to reconstitute some of the western lines around 1912. The spur line to the mill was not electrified.

The bridge, built in 1910 across the Clark Fork was originally wooden, hence the cover over it to protect it from the weather. It was refurbished in 1934 and given steel supports in the 1950s. The cover was removed, and now it became known as the Duck Bridge as hunters used to shoot ducks from it. Many Bonner area children swam near the bridge.  The Milwaukee went bankrupt in 1977 and the track was abandoned in 1978 and the bridge was removed shortly thereafter.