Era
20th century
440
1900-1999
201
19th century
106
21st century
57
1800-1899
25
2000-2099
25
1800-1999
24
1927-1993
21
Revolution, 1910-1920
19
Civil War, 1861-1865
15
1846-1950
14
1951-
14
1900-2099
12
1900 - 1999
10
1944-
10
1945-1989
9
1991-2000
8
1910-1946
7
1930-
7
1933-1945
7
1800-1950
6
1933-
6
1933-2023
6
1946-
6
1951-1960
6
1957-
6
1980-
6
1981-1990
6
To 1846
6
To 1899
6
1821-1861
5
1848-
5
1865-1950
5
1915-1999
5
1918-1945
5
1929
5
1960-1980
5
1989-1993
5
Punitive Expedition into Mexico, 1916
5
Since 1900
5
1815-1861
4
1867-1910
4
18th century
4
1908-1973
4
1938-
4
1945-
4
1948-
4
1949-
4
1952-
4
1971-1980
4
more ...