I think this picture is of Giant Hogweed (Heracleum mantegazzianum) which is, unfortunately, fairly common in the Pacific Northwest.
http://wisplants.uwsp.edu/scri...
Heracleum mantegazzianum and Conium maculatum are in the same family (Apiaceae) and both are sometimes referred to by the common names of "cowbane" and "hemlock" so it's not surprising that there might be some confusion with them