Era
1887-1986
28
20th century
17
19th century
16
Civil War, 1861-1865
16
Cretaceous
14
1924-
9
1775-1865
8
1991-
8
Eocene
6
1864-1946
4
1865-1950
4
Colonial period, ca. 1600-1775
4
Paleozoic
4
18th century
3
1929-1968
3
1951-
3
1962-2007
3
Tertiary
3
1864-1939
2
1884-1915
2
1977-1981
2
21st century
2
Devonian
2
Pleistocene
2
Quaternary
2
Revolution, 1775-1783
2
Silurian
2
-1913
1
1696-1785
1
1703-1791
1
1780-1856
1
1803-1879
1
1804-1863
1
1808-1844
1
1809-1893
1
1810-1885
1
1812-1883
1
1812-1891
1
1823-1862
1
1828-1864
1
1834-1907
1
1835-1930
1
1837-1910
1
1845-1922
1
1847-1865
1
1847?-1913
1
1855-1926
1
1861-1865
1
1871-1951
1
1874-1960
1
more ...