Emmenegger Nature Park contains 93 acres. Possum Woods Conservation Area, located adjacent to Emmenegger Nature Park, contains an additional 15 acres. The combination of the two areas totals approximately 108 acres.

Originally, the area was part of a large estate owned by members of the Lemp family. This family owned a large St. Louis brewery around the turn of the 20th century.

Over the last 100 years, the area was used as an exotic animal breeding area for the St. Louis Zoo, a riverside resort and a public swimming pool and tennis club.

Russell E. Emmenegger, a prominent real estate developer, purchased the land in the 1970's and donated part of the property to the City of Kirkwood. The property is leased by the Department of Conservation, and is currently operated in partnership between MDC and the City of Kirkwood.

The topography of the area allows for a diverse mix of upland hardwoods along the ridges and bottom land species in the valley and along the Meramec River, which is located along the western boundary of the area. Upland hardwood forest tree species includes white oak, red oak, post oak, shagbark hickory, sugar maple, and many others. The understory trees include roughleaf dogwood, redbud, and pawpaw. Species in the bottomland areas include elm, boxelder, silver maple, American sycamore and white oak, among others.