The city originally built the North Avenue Dam in 1891 to control flooding and provide energy for mills, tanneries, factories and breweries. This also created a large recreation area for swimming and boating just north of the dam. Before it was removed in 1997, just eight species of fish were found above the dam. After the removal, 30 species were found, including stonerollers, darters, smallmouth bass, walleyes and northern pike.
Today, osprey, herons and otter populate the river banks, and in the spring and fall, lake trout and salmon swim upstream as far as Grafton to spawn.