The presence of inland grasslands on the Atlantic coastal plain, including an extensive “tall-grass prairie” at Hempstead Plains on Long Island, NY, remote from the “prairie peninsula”, has never been explained. In 2008, surveys of Homoptera: Auchenorrhyncha on prairie grasses were conducted from Long Island north to Maine. Multiple prairie-endemic species were found on glades from Rhode Island to New Hampshire, including flightless Cercopidae found only on sand plains. The ranges of 12 species were compared to those of another 50 Cercopidae, Cicadellidae, and Caliscelidae specializing on 15 genera of grasses found in tall-grass prairies. Most support evidence that sand-adapted prairie grasses constitute the easternmost extent of the prairie peninsula that could have come eastward to glaciated New England by following recent glacial moraines before forests re-established themselves in the area 11,000–9000 years ago. This periglacial ecosystem was distinct from a grassland ecosystem in the southeastern states that expanded northwards to Long Island and Cape Cod, MA.