The Willimantic River Hiking Trail follows the river seven miles north from Mansfield to Tolland. I hiked the length of the trail in spring 2021 and was able to easily navigate the entire length. Surprisingly the first view of the river is over a half mile into the trail and the first time you can touch the water is over two miles in.
Unfortunately the Willimantic River Alliance seems to be active, so development of the trail is on pause. However, hopefully at some point in the future the trail can be extended in either direction.