Era
20th century
27
19th century
24
1876-1950
18
Civil War, 1861-1865
10
To 1876
9
1951-
6
1840-1931
5
Cretaceous
5
1817-1879
4
1929
4
1830-1899
3
1842-1907
3
1843-1942
3
1871-1945
3
Jurassic
3
Quaternary
3
Tertiary
3
1794-1860
2
1851-1926
2
1864-1939
2
1867-1932
2
1869-1934
2
1871-1941
2
1886-1980
2
1901-
2
21st century
2
Cenozoic
2
Eocene
2
Mesozoic
2
Paleozoic
2
-1914
1
-1919
1
-1935
1
1803-1885
1
1809-1869
1
1812-1878
1
1812-1901
1
1814-1897
1
1817-1892
1
1820-1891
1
1821-1894
1
1825-1878
1
1825-1894
1
1825-1901
1
1826-1878
1
1826-1914
1
1830-1914
1
1831-1874
1
1831-1881
1
1833-1895
1
more ...