Nodding trillium is the widely accepted name for this species.
But there are several other species with nodding habits that covet that name. In an apparent attempt to be unambiguous, the USDA Plants site and others are now calling this whip-poor-will flower. Their attempt to find a unique label is of course doomed in the muddled world of common names. When I Googled whip-poor-will flower the first item that came up described it as a red flower. Nodding trillium is our most northern species, occurring in woods in CT, DE, IA, IL(E), IN(E), MA, MD, ME, MI, MN, ND, NH, NJ, NY(V), OH(X), PA, RI, SD, VA, VT, WI, WV, MB, NB, NF, NS, ON, PE, QC, SK, and on SPM. Montmorency Co MI, 5/26/12.