The top subject headings in the DPLA are:
[(u'Plantae', 10094),
(u'Photographs', 8552),
(u'Dicotyledonae', 6677),
(u'Asteraceae', 3873),
(u'Asterales', 3792),
(u'United States', 3612),
(u'Portraits', 3454),
(u'Texas', 3023),
(u'Pteridophyte', 2772),
(u'Animalia', 2699),
(u'California', 2607),
(u'Books', 2535),
(u'Memorial books (Holocaust)', 2489),
(u'Ethnic relations', 2381),
(u'Holocaust, Jewish (1939-1945)', 2380),
(u'Places', 2360),
(u'Maps', 2149),
(u'Georgia', 2114),
(u'Buildings', 2106),
(u'Maryland', 1888),
(u'Polypodiales', 1856),
(u'Politics and government', 1842),
(u'Jews', 1818),
(u'Landscape and Nature', 1814),
(u'Governors', 1768),
(u'Geography and Maps', 1707),
(u'History', 1699),
(u'Maryland--Politics and government', 1691),
(u'Anthropology', 1689),
(u'Men', 1666),
(u'Governors--Maryland', 1650),
(u'Architecture', 1585),
(u'People', 1578),
(u'Arthropoda', 1477),
(u'Ehrlich, Robert L., 1957-', 1414),
(u'Women', 1381),
(u'Los Angeles', 1339),
(u'Pictorial works', 1280),
(u'Exhibitions', 1237),
(u'Students', 1154),
(u'Insects', 1114),
(u'Insecta', 1112),
(u'North Carolina', 1095),
(u'Ethnology', 1046),
(u'Census', 1043),
(u'Census--Maps', 1043),
(u'Statistical areas', 1043),
(u'Census blocks', 1028),
(u'Streets', 960),
(u'Dwellings', 911),
(u'Hymenoptera', 868),
(u'Fabaceae', 867),
(u'Rosales', 865),
(u'Apidae', 851),
(u"New York World's Fair (1939-1940)", 838),
(u'Social Life and Customs', 821),
(u'Utah', 811),
(u'Valley Times Collection photographs', 805),
(u'Automobiles', 797),
(u'Universities & colleges', 771),
(u'Provo (Utah)', 766),
(u'Atlanta', 752),
(u'Portrait collection', 751),
(u'Crowdsourcing Project', 699),
(u'Agricultural education', 671),
(u'University of Georgia. College of Agricultural and Environmental Sciences',
665),
(u'Children', 661),
(u'Events', 655),
(u'Archaeology', 654),
(u'Surveys', 641),
(u'Maps, Topographic', 638),
(u'Elevations', 637),
(u'Historic sites', 637),
(u'Agricultural education--Georgia', 630),
(u'Topographic maps', 628),
(u'Texas--Maps, Topographic', 628),
(u'Topography', 628),
(u'Geologic surveys', 624),
(u'Survey maps', 624),
(u'Geologic maps', 624),
(u'Texas--Surveys', 624),
(u'Quadrangle maps', 624),
(u'Chordata', 620),
(u'Education', 613),
(u'Pepperdine University', 595),
(u'National Museum of Natural History (UNITED STATES)', 594),
(u'Monocotyledonae', 585),
(u'Herald-Examiner Collection photographs', 572),
(u'African Americans', 572),
(u'Black-and-white photographs', 566),
(u'Type Register', 564),
(u'University of California, San Diego', 562),
(u'Portrait photographs', 549),
(u'Arts and Crafts', 533),
(u'20th century', 529),
(u'South Carolina', 522),
(u'Guiana Shield', 513),
(u'Group portraits', 512),
(u'THC', 505),
(u'Macior, L. W', 502),
(u'Euphorbiaceae', 494),
(u'Euphorbiales', 494),
(u'Transportation', 478),
(u'Theater', 464),
(u'Greenville', 460),
(u'Agriculture', 450),
(u'Historical buildings', 449),
(u'Fishes', 445),
(u'Schools', 433),
(u'Houses', 430),
(u'Faculty', 426),
(u'Wisconsin', 425),
(u'Aerial photographs', 425),
(u'Trees', 407),
(u'Sports and Recreation', 404),
(u'Myrtales', 404),
(u'Polypodiaceae', 402),
(u'Native Americans', 401),
(u'Actinopterygii', 399),
(u'Pteridaceae', 397),
(u'University of California, San Diego--History', 397),
(u'Historic buildings', 393),
(u'Japan', 384),
(u'World War, 1939-1945', 374),
(u'Automobile racing drivers', 370),
(u'Employees', 366),
(u'University of California, San Diego--Pictorial works', 366),
(u'Family', 362),
(u'New York City Ballet', 362),
(u'Public libraries', 359),
(u'(1990-current) Contemporary', 359),
(u'University of Southern California', 359),
(u'Business, Economics and Finance', 356),
(u'West Indies Project', 353),
(u'Art', 351),
(u'Ski Archives', 347),
(u'Parks', 346),
(u'Indianapolis Motor Speedway (Speedway, Ind.)', 342),
(u'Steele, Michael S., 1958-', 338),
(u'Individuals', 337),
(u'Paleogeneral', 333),
(u'Protista', 330),
(u'Sports', 330),
(u'Washington (State)', 326),
(u'Dallas', 326),
(u'Parades', 326),
(u'Los Angeles Herald-Examiner photographs', 323),
(u'Festivals', 322),
(u'1951-1960', 316),
(u'Automobiles, Racing', 310),
(u'Football', 306),
(u'Hotels', 306),
(u'Men--California--Los Angeles', 303),
(u'Horses', 303),
(u'University of California, San Diego--People', 302),
(u'Railroads', 299),
(u'Census county divisions', 299),
(u'Construction', 298),
(u'Green River Fm', 297),
(u'Aerial views', 295),
(u'Universities and colleges', 295),
(u'Presidents', 293),
(u'Clubs and Organizations', 293),
(u'Roads', 291),
(u'Baseball', 290),
(u'Churches', 288),
(u'Museum exhibits', 288),
(u'River Basin Survey', 286),
(u'Mississippi', 284),
(u'Onagraceae', 284),
(u'Kohls, David, (UNITED STATES)', 283),
(u'Customs', 282),
(u'Milwaukee', 281),
(u'Demonstrations', 274),
(u'World War II', 274),
(u'Mountains', 273),
(u'Crowds', 269),
(u'Rivers', 266),
(u'Dryopteridaceae', 263),
(u'University of California, San Diego--Events', 261),
(u'Military and War', 261),
(u'Cyperales', 259),
(u'Celebrations', 259),
(u'Buildings, structures, etc', 257),
(u'Athletics', 253),
(u'Theatrical productions', 251),
(u'Perciformes', 251),
(u'Danmission', 247),
(u'Women--California--Los Angeles', 247),
(u'1961-1970', 247),
(u'Artworks', 247),
(u'Clothing and dress', 240),
(u'Malacostraca', 240),
(u'Museum exhibits--Texas--Dallas', 239),
(u'Annelida', 238),
(u'Georgia Institute of Technology', 236),
(u'Atlanta (Ga.)', 233),
(u'Portraits, Group', 229),
(u'College campuses', 229),
(u'Bridges', 228),
(u'Theaters', 228),
(u'Domestic Animals', 223),
(u'Wars', 222),
(u'Music', 222),
(u'Restaurants', 222),
(u'Baseball players', 221),
(u'Colleges and Universities', 221),
(u'WWII', 221),
(u'Boys', 220),
(u'Illinois', 220),
(u'Faust, M. A', 219),
(u'Farm life', 219),
(u'Mexican Americans', 219),
(u'Awards', 217),
(u'Farm life--Mississippi', 213),
(u'Libraries', 213),
(u'Atlanta (Ga.)--History--20th century', 212),
(u'Georgia Institute of Technology--History--20th century', 212),
(u'Hymenophyllales', 207),
(u'Hymenophyllaceae', 207),
(u'Males', 206),
(u'King, R. M', 206),
(u'Portrait', 206),
(u'Police', 206),
(u'Basketball', 204),
(u'Dance', 204),
(u'Competitions', 202),
(u'Pacific Ethnobotany', 202),
(u'Lost architecture', 200),
(u'Politicians', 198),
(u'Interiors', 198),
(u'Chicanos', 196),
(u'Posters', 196),
(u'Malvales', 196),
(u'Personnel', 195),
(u'Photography', 191),
(u'Ehrlich, Kendel S., 1961-', 191),
(u'Pyrrophyta', 191),
(u'Portrait photographs--1951-1960', 191),
(u'Athletes', 190),
(u'Prehistoric', 190),
(u'Aspleniaceae', 190),
(u'Cyatheales', 190),
(u'Portrait photographs--1961-1970', 189),
(u'Smithsonian Tropical Research Institute', 187),
(u'Girls', 187),
(u'Riding', 187),
(u'Fort Worth', 185),
(u'Smithsonian Institution', 184),
(u'National Cutting Horse Association', 184),
(u'World Science Fiction Convention', 183),
(u'Science fiction fans', 183),
(u'Cutting horses', 183),
(u'Mexican American art', 182),
(u'Law schools', 182),
(u'Signs and signboards', 182),
(u'Cities and towns', 181),
(u'Chicano art', 179),
(u'Portrait photography', 179),
(u'Poaceae', 178),
(u'Actors', 178),
(u'Architecture, Modern', 178),
(u'Government and Law', 177),
(u'NCHA', 177),
(u'Fosberg, F. R', 177),
(u'Snowboards and snowboarding', 176),
(u'Cemeteries', 176),
(u'Columbia (S.C.)', 176),
(u'Associations, institutions, etc.', 176),
(u'Derbies', 173),
(u'Cutting horses--Competitions--Texas--Fort Worth', 173),
(u'Architecture, Modern--20th century', 172),
(u"Young Men's Christian associations", 171),
(u'Pacific Islands and Onagraceae', 171),
(u'DRG maps', 170)]