The first power dam was built between 1869 and 1871. It started on the south bank of Sylvan Slough on the river bank at Moline, ran along the east shore of Sylvan Island, then crossed the channel of Sylvan Slough to connect with Arsenal Island. Water was drawn in from the Sylvan Slough channel, and exited a 2,100 foot long tailrace canal that was built as part of the 1871 project.
In 1898 and 1899, the 1871 project was removed and a new power plant was built at its current location at the east end of the tailrace canal. This new dam and powerhouse did not cross Sylvan Slough. Rather, a second dam and powerhouse for the Rock Island Arsenal was built across Sylvan Slough to support the US Army factories.
The 1899 power plant was again removed and rebuilt in 1941 and 1942. Those buildings exist today, and are still in use generating hydro power for the Quad Cities area. The generators have been upgraded several times, however, so the plant produces vastly more power today than when it opened in 1942.
The canal itself was cut from limestone, and the bottom is bedrock, which happens to be very near the surface in that area. This shallow bedrock is the reason for the rapids and cascades existing in the Quad Cities area. The photo above is looking upriver from the Sylvan Wagon bridge towards the power plant. The photo below is looking downriver, with the final photo being the location where the canal rejoins Sylvan Slough. The slough flows from the right, around the corner, and exits the back of the photo. The canal enters from the front. One can see the rock outcroppings that are left from blasting the canal path.