I identified a new plant on my bike ride on Saturday (see Summer Re-runs). Included for your delectation are two shots of the redundantly named Broad-leaf waterleaf (Hydrophyllum canadense).
The first shot shows the leaves, which look very much like those of the maple tree.
This second shot is a closeup of the blooms, which are just opening. You can better see their feathery appearance.
It's a native plant, and you can see its distribution map at the US Wildflower site.