The Purple Loosestrife, blooming along Portage Creek, caught my eye first. While its flowers are pretty, it's an invasive exotic that easily dominates wet habitats. Continuing along the trail at Bicentennial Park, I noticed many other purple flowers: Red Clover, Swamp Milkweed, Chicory, Bergamot, and Blue Vervain. All the purple blossoms primed me to see a native flower I'd never noticed before: Purple Fringed Orchid.
Purple Fringed Orchids (Platanthera psycodes) grow in moist soil, scattered throughout the eastern US and Canada. They are protected species in parts of their range. (It's possible this plant was the very similar, and closely related, Platanthera grandiflora.) I was surprised to see such a beautiful wildflower in such an ordinary place.