Era
20th century
11
1900-1999
6
1981-
6
1900 - 1999
4
Since 1981
4
1866-1936
2
1899-1961
2
Miocene
2
Pliocene
2
Quaternary
2
To 1803
2
1800-1900
1
1861-1865
1
1861-1865 (Guerre de Sécession)
1
1865-
1
1865-1950
1
1875-1929
1
1911-1983
1
1924-1997
1
1948-
1
1951-
1
19th century
1
Cenozoic
1
Civil War, 1861-1865
1
Florida
1
Pleistocene
1
Since 1951
1
To 1821
1