20th century 9,121 View Records 19th century 4,168 View Records 21st century 1,568 View Records 18th century 1,218 View Records 1933-1945 1,076 View Records 1945-1989 1,011 View Records 1564-1616 962 View Records Civil War, 1861-1865 935 View Records 1945- 819 View Records Cretaceous 802 View Records 17th century 711 View Records Revolution, 1775-1783 482 View Records 1969- 465 View Records 16th century 448 View Records Tertiary 428 View Records 1989- 408 View Records Quaternary 395 View Records 2001-2009 362 View Records Early modern, 1500-1700 362 View Records Colonial period, ca. 1600-1775 350 View Records 2009- 341 View Records Precambrian 330 View Records 1946- 325 View Records Paleozoic 322 View Records 1945-1953 297 View Records Cenozoic 283 View Records 1945-1955 273 View Records 1953-1961 271 View Records 1991- 262 View Records To 1500 261 View Records 1951- 248 View Records Permian 239 View Records 1809-1865 237 View Records 1980- 237 View Records 1929 232 View Records 1960- 231 View Records 1981-2001 231 View Records Eocene 231 View Records 1993-2001 226 View Records 1955-1965 223 View Records 1918-1945 222 View Records Jurassic 209 View Records Mesozoic 209 View Records 1882-1945 205 View Records 1917-1963 204 View Records Pennsylvanian 204 View Records Miocene 194 View Records Ordovician 188 View Records Pleistocene 179 View Records 1947- 173 View Records 1913-1994 171 View Records 1949- 171 View Records Devonian 170 View Records 2000- 164 View Records 1939- 163 View Records 1608-1674 162 View Records 1939-1945 162 View Records 1948- 160 View Records 1961-1969 160 View Records Appropriations and expenditures, 2000 160 View Records Mississippian 160 View Records -1400 154 View Records Appropriations and expenditures, 2001 149 View Records 1783-1865 148 View Records 1950- 148 View Records Triassic 145 View Records 1882-1941 144 View Records 1961-1970 138 View Records 1979- 136 View Records Appropriations and expenditures, 2013 135 View Records 1965- 133 View Records Appropriations and expenditures, 2006 132 View Records 1743-1826 131 View Records 1812-1870 131 View Records Appropriations and expenditures, 1998 131 View Records 1981-1989 129 View Records 1866-1895 126 View Records 1960-1980 126 View Records Appropriations and expenditures, 1999 126 View Records 1952- 125 View Records Appropriations and expenditures, 2004 125 View Records 1954- 123 View Records Cambrian 122 View Records Appropriations and expenditures, 2002 120 View Records Appropriations and expenditures, 2007 120 View Records 1990- 119 View Records 1991-2000 118 View Records Appropriations and expenditures, 2012 118 View Records Pliocene 117 View Records To 1775 117 View Records 1897-1962 116 View Records Middle English, 1100-1500 115 View Records 1889-1945 114 View Records Appropriations and expenditures, 2014 114 View Records 1934- 113 View Records 2001- 113 View Records Revolution, 1789-1799 113 View Records 1775-1865 110 View Records 1890-1969 110 View Records 1955- 110 View Records