G - Geography, Anthropology, Recreation 480 Q - Science 46 C - Historical Sciences 19 S - Agriculture 9 H - Social Science 2 A - General Works 1 M - Music 1 T - Technology 1 see all ...

Geological Survey (U.S.) 997 Pennsylvania Bureau of Topographic and Geologic Survey 217 Pennsylvania Department of Internal Affairs 167 Zandle, Gerald L 144 Bromery, Randolph W (Randolph Wilson), 1926-2013 81 Bromery, Randolph Wilson, 1926- 77 National Wetlands Inventory (U.S.) 46 Wood, Gordon H (Gordon Harry), 1919- 44 Henderson, John R 31 Pennsylvania Department of Conservation and Natural Resources 31 United States Soil Conservation Service 29 Pennsylvania Department of Environmental Resources 25 Chester County Water Resources Authority 24 Drake, Avery Ala, 1927- 22 United States Bureau of the Census 21 Williams and Heintz Map Corporation 18 Epstein, Jack Burton, 1935- 17 Arndt, Harold H 15 Trexler, J. Peter, 1926- 14 McManus, B. Craig 13 Roen, John B 13 Schweinfurth, Stanley P 13 Delaware River Basin Commission 12 Kent, Bion H (Bion Huntley), 1925- 12 Pennsylvania Department of Highways 12 Geological Survey of Pennsylvania 11 Boynton, G. R 10 Boynton, G. R (George Robert), 1935- 10 Natoff, Nora C 10 Pittillo, D. R 10 see all ...

English 1,219 Undetermined 1

Maps 1,088 Topographic maps 406 Databases 33 Geological maps 32 Maps, Topographic 25 Statistics 19 Census, 1990 16 Thematic maps 14 Cartes géographiques 13 Tourist maps 13 CD-ROMs 8 Road maps 7 geological maps 7 Cartes géologiques 6 Maps, Physical 5 Physical maps 5 Charts, diagrams, etc 4 Remote-sensing maps 3 Atlases 2 Bathymetric maps 2 Cartes thématiques 2 Index maps 2 Indexes 2 Observations 2 Tours 2 thematic maps 2 Bradford Region (Pa.) 1 Cartes géologiques 1 Cartes topographiques 1 Census data 1 see all ...

Mississippian 5 Pre-Quaternary 4 1980 2 Silurian 2 1800-1899 1 1863 1 19th century 1 Devonian 1 From 405 to 425 million years ago 1 Revolution, 1775-1783 1 see all ...