Inventories of macrofungal species in four National Capital Region Network parks (Antietam National Battlefield, Catoctin Mountain Park, Chesapeake and Ohio Canal National Historical Park, and Prince William Forest Park) were conducted in 2005 and 2006 through repeated visits to permanent plots and forays. A total of 256 fungal taxa were identified. Species of Marasmius, Polyporus, Trametes, Crepidotus, Pleurotus, and Schizophyllum were found in every Park. Although there were similarities among Parks, each was unique. Prince William Forest Park had the greatest macrofungal diversity (148 taxa) and abundance of fruiting bodies (344 collected). Catoctin Mountain Park was nearly as rich (116 taxa from 329 collections). Chesapeake and Ohio Canal National Historical Park and Antietam National Battlefield were rich in Schizophyllum and Marasmius, but included fewer fungal taxa overall (54 from 126 collections and 53 from 105 collections, respectively). This document presents the lists of taxa found at these locations. A database developed by Geoffrey Sanders, Data Manager, National Capital Region, Center for Urban Ecology, contains additional information about the collections. Representative dried specimens and their corresponding in situ photographs have been vouchered and deposited with the National Park Service to allow future mycological studies. Given the tremendous diversity of fungi known to be present in the mid-Atlantic region, further inventory work would expand the understanding of macrofungi in these Parks.