Parfrey's Glen State Natural Area is a protected sandstone gorge in Devil's Lake State Park near Merrimac, Wisconsin, cut into the south flank of the Baraboo Hills and shaped by a cold stream flowing through a narrow, shaded valley. Named for Robert Parfrey, it became Wisconsin's first State Natural Area in 1952, aided by Norman Carter Fassett's efforts to preserve it for scientific research. Its cool, moist microclimate supports mosses, ferns, northern plants, rare species, uncommon insects, and state-threatened birds. A round-trip trail and the Ice Age Trail pass through the area, where the final approach now follows the streambed after storm damage destroyed the boardwalk.