I found this one pretty quick because of its bright yellow color. It was near most of the trails in open spaces.
Ranunculus occidentalis (western buttercup) is a species of buttercup found in the western United States and Canada. Its distribution extends from Alaska through British Columbia and Alberta to central California. The flower can be seen in open meadows, forests, and other generally flat areas up to an elevation of 2,200 metres (7,200 ft).