I think this is some species of hairstreak, I was going to say a brown elfin, but my guide doesn't show or mention those irridescent green scales near the body on the underwing.

I think the plant is a Mountain Parsley (Harbouria trachypleura). We found both in the Forgotten Valley in Goldengate State Park (west of Golden, Colorado). Each blossom is about 1/8" (.3 cm) long and so the butterfly is just shy of the 1" (2.5 cm) range.