At first I thought it was a Cinquefoil. Perhaps Tall Cinquefoil (Potentilla arguta), but Tall Cinquefoil has white flowers. Or Pennsylvania Cinquefoil (Potentilla pectinata), but the flowers of Pennsylvania Cinquefoil grow in a cyme rather than on a spike and the leaflets of Pennsylvania Cinquefoil are much more deeply dissected. Then I thought it might be Pacific Silverweed (Argentina egedii), but each flower of Pacific Silverweed grows on a separate stalk. Flipping through all of the yellow flower pictures in a field guide was what saved the day.
The leaves are alternate and pinnately-divided with 5-9 large, coarsely-toothed leaflets with tiny leaflets between. The flowers are deep yellow with five petals and look like cinquefoil flowers except that the flower petals are not notched at the tip as with some cinquefoils. The flowers grow on spikes and are not densely packed as they are with Roadside Agrimony (Agrimonia striata).
