Era
20th century
275
19th century
65
1900-1999
63
21st century
57
2000-2099
31
1975-
30
1800-1899
21
Civil War, 1861-1865
20
1877-1964
16
1980-
16
18th century
11
1861-1865
9
1865-1918
8
To 1964
8
1868-1963
7
1929-1968
7
2001-2009
7
Revolution, 1775-1783
7
1809-1865
6
1818-1895
6
1863-1877
6
1973-2020
6
1989-
6
1993-
6
Colonial period, ca. 1600-1775
6
1700-1799
5
1783-1865
5
1800-1999
5
1856-1915
5
1946-
5
Since 1975
5
Since 1980
5
1858-1942
4
1900 - 1999
4
1901-1981
4
1908-1997
4
1921 September 27-
4
1941-1955
4
1944-
4
1945-1989
4
1980-2020
4
2009-2017
4
1797-1874
3
1800-1859
3
1813-1865
3
1909-1993
3
1913-1921
3
1918-1961
3
1921-1923
3
1922-2012
3
more ...