Cretaceous 34
To 1848 34
Permian 27
20th century 22
Jurassic 22
Pennsylvanian 22
1848- 20
Tertiary 15
19th century 14
Cenozoic 10
Paleozoic 10
Civil War, 1861-1865 9
Quaternary 9
Triassic 9
1848-1950 8
Precambrian 8
Mississippian 7
1846-1850 3
1887-1986 3
Conquest, 1519-1540 3
Ordovician 3
Pleistocene 3
Pliocene 3
To 1876 3
1549?-1624 2
1735-1788 2
17th century 2
1845-1893 2
1859-1944 2
1864-1945 2
1866-1895 2
1877-1943 2
1879-1962 2
1917-1957 2
1929 2
21st century 2
Cambrian 2
Carboniferous 2
Devonian 2
Mesozoic 2
Paleocene 2
Pre-Quaternary 2
To 1846 2
-1792 1
-1847 1
1182-1226 1
1624-1687 1
1643-1704 1
1671-1720 1
1672-1720 1
1673-1737 1
1765- 1
1765-1850 1
1793-1867 1
1794- 1
1803?-1852 1
1814-1888 1
1816-1886 1
1818-1875 1
1818-1889 1
1832-1900 1
1833-1925 1
1838-1915 1
1840-1921 1
1842-1902 1
1845-1938 1
1850-1928 1
1850-1937 1
1859?-1929? 1
1871-1951 1
1873-1966 1
1874-1958 1
1874-1960 1
1876-1936 1
1876-1954 1
1880-1958 1
1881-1931 1
1881-1973 1
1883-1977 1
1885-1930 1
1886-1956 1
1886-1988 1
1888-1935 1
1896-1959 1
1897-1964 1
1898-1955 1
18th century 1
1900-1978 1
1902-1995 1
1903-1992 1
1914-1994 1
1918-2006 1
1932- 1
1940-2023 1
1944- 1
1985- 1
Descubrimiento y conquista, 1517- 1521 1
Holocene 1
Modern period, 1500- 1
Neogene 1