purchased the site from W. R. Jeffers, Jr. in 1966 and it was added to the National Register of Historic Places in 1970. It is maintained by the Minnesota Historical Society and is open to the public between May and September. The site is bracketed by two important tracts of tallgrass prairie: Rock Ridge Prairie Scientific and Natural Area to the northwest and Red Rock Prairie, a preserve of The Nature Conservancy, to the east. Here federally threatened prairie bush clover is found, as well as big bluestem, Indian grass, gray-headed coneflower, Maximilian's sunflower, cordgrass and coreopsis. The upland sandpiper, regal fritillary and Poweshiek skipper can be found on these prairies. The visitor center is open from May through September and features hands-on exhibits and a multimedia presentation about the site. Daily natural and cultural history programs are offered about such topics as archaeology, how Native Americans made and used the atlatl, a travois and cordage, and prairie wildlife and plants. Astronomy at Jeffers Petroglyphs The Starry Night, Prairie Night event is held annually in the park. During this time the park manager allows amateur astronomers to use the park and facilities. Many amateur astronomers attend this event and several members bring their telescopes and allow, and often encourage, others to share their views of the night sky. This site is valued not only because of its historic nature but also because of its dark night skies. The site is much darker than most populated areas in Minnesota and is rated green by the Clear Sky Chart. References Further reading External links Minnesota Historical Society: Jeffers Petroglyphs Friends of the Jeffers Petroglyphs Historic Site Archaeological sites on the National Register of Historic Places in Minnesota Minnesota Historical Society Minnesota state historic sites Museums in Cottonwood County, Minnesota Native American history of Minnesota Native American museums in Minnesota Petroglyphs in Minnesota Religious places of the indigenous peoples of North America Protected areas of Cottonwood County, Minnesota National Register of Historic Places in Cottonwood County, Minnesota Quartzite formations