On an April 9, 1986 field trip to the Congaree Swamp National Monument (CSNM) in Richland County, South Carolina, the senior author collected from the floodplain near Weston Lake a Carex that looked remarkably like Carex socialis Mohl. and Schweg., a species hitherto thought to be endemic to the lower Mississippi River Valley region of the Midwest. It became evident after closer observation that the specimen was Carex socialis; a determination was later confirmed by an authority on the species, John Schwegman. A survey of the literature, including Godfrey and Wooten (1979) and Radford et al (1968), and communication with botanists in natural heritage programs in the Southeast revealed an absence of records of this taxon. This makes the collection of Carex socialis the first record for the State of South Carolina, and more significantly, first for the Atlantic Coastal Plain region as well.