I think this is White Geranium. According to the Central Rocky Mountain Wildflowers Falcon Guide, it is a medicinal herb that can be used to treat diarrhea, dysentery, ulcers, and hemorrhoids, and to stop bleeding (211). It’s found in shady woodlands, plains, valleys, montane, and lower subalpine zones. This is exactly where I found it! This, and the flowers that will follow, were photographed on a weekend trip to Citadel of Rocks, Idaho.