20th century 85
19th century 71
1775-1865 52
Civil War, 1861-1865 32
1951- 31
1865-1950 18
1865- 16
1865-1877 15
Colonial period, ca. 1600-1775 14
1897-1962 13
Revolution, 1775-1783 13
Cretaceous 12
1865-1951 10
Tertiary 8
1890-1980 6
18th century 6
21st century 6
Eocene 6
1783-1865 4
1857-1861 4
Miocene 4
Ordovician 4
Quaternary 4
To 1775 4
1863-1877 3
1909-2001 3
1911-1983 3
1918- 3
1945- 3
16th century 2
1789-1869 2
1794-1865 2
1806-1870 2
1807-1870 2
1815-1861 2
1835-1910 2
1865-1900 2
1865-1933 2
1873-1945 2
1877-1934 2
1897-1966 2
1905-1989 2
1917-1967 2
1924- 2
1929 2
1941-1955 2
1945-1989 2
1964-1975 2
1981-2001 2
1989- 2
Jurassic 2
To 1863 2
To 1900 2
War of 1812 2
approximately 1500-1542 2
-1855 1
1564-1616 1
1718-1779 1
1725-1807 1
1732-1799 1
1739-1823 1
1743-1826 1
1767-1845 1
1789-1851 1
1790-1866 1
1790-1866, 1
17th century 1
1807-1864 1
1811-1884 1
1814-1863 1
1814?-1884 1
1815 or 1816- 1
1815-1875 1
1816-1894 1
1818-1867 1
1820-1890 1
1822-1903 1
1822-1909 1
1823-1862 1
1823-1886 1
1832- 1
1833-1902 1
1835-1930 1
1843-1913 1
1843-1914 1
1844-1925 1
1846- 1
1849-1923 1
1860 1
1862-1931 1
1865-1898 1
1865-1918 1
1869-1940 1
1870-1937 1
1874-1932 1
1874-1956 1
1877-1964 1
1878-1961 1
1882-1941 1
1882-1945 1