Era
20th century
114
Civil War, 1861-1865
60
1981-2001
32
21st century
31
19th century
28
Revolution, 1775-1783
19
Cretaceous
18
1953-1961
13
1993-2001
13
War of 1812
12
1924-
11
1945-
11
2009-
11
1945-1953
10
2001-2009
10
1945-1989
9
1946-
9
World War, 1939-1945
9
1969-1974
8
Devonian
8
Paleozoic
8
Precambrian
8
18th century
7
1977-1981
7
1981-1989
7
Tertiary
7
1890-1969
6
1913-1994
6
1965-
6
1981-1993
6
Mesozoic
6
Vietnam War, 1961-1975
6
1809-1865
5
1961-1963
5
1980-2020
5
1989-
5
Cenozoic
5
Jurassic
5
Quaternary
5
World War, 1914-1918
5
1913-2006
4
1945-1975
4
1976-2002
4
American Invasion, 1989
4
Cambrian
4
Korean War, 1950-1953
4
Mississippian
4
Tiananmen Square Incident, 1989
4
1783-1815
3
1917-2002
3
more ...