Era
20th century
148
19th century
44
Devonian
24
1858-1919
21
Revolution, 1775-1783
14
1951-
13
18th century
12
1775-1865
11
1865-1950
11
Colonial period, ca. 1600-1775
11
Silurian
11
21st century
10
1898-1951
9
Cretaceous
9
1782-1862
7
1757-1804
6
1822-1913
6
1882-1945
6
Civil War, 1861-1865
6
Pleistocene
6
17th century
4
1801-1848
4
To 1775
4
1775-1783
3
1884-1962
3
1933-1945
3
1942-
3
1949-
3
1592-1672
2
1697-1746
2
1734-1821
2
1752-1816
2
1783-1789
2
1815-1861
2
1820-1841
2
1827-1901
2
1865-1898
2
1881-1955
2
1881-1973
2
1882-1947
2
1892-1969
2
1908-1984
2
1914-1970
2
1915-1953
2
1917-1973
2
1918-1953
2
1921-1930
2
1926-1966
2
1928-2011
2
1935-1964
2
more ...