Gensburg-Markham Prairie is a 105.6-acre remnant of high-quality tallgrass prairie in Markham, south of Chicago, within the larger Indian Boundary Prairies. Formed on a sandy beach left by postglacial Lake Chicago at the end of the Wisconsin glaciation, its damp, poorly drained sandy loam resisted farming and later development, helping native prairie survive. In 1971, the Gensburg family donated a central 60-acre parcel to Northeastern Illinois University, which led restoration as invasive plants had badly degraded the site. Guided by Robert Betz and aided by controlled burns, recovery advanced, and the prairie was dedicated an Illinois Nature Preserve in September 1980. It remains a rare Chicago-area prairie supporting native species, including Henslow’s sparrow.