Era
Civil War, 1861-1865
11
19th century
7
1884-1972
6
Precambrian
4
1835-1910
3
1837-1865
3
1865-1950
3
20th century
3
Pennsylvanian
3
1770-1838
2
1822-1885
2
Cambrian
2
Carboniferous
2
Mississippian
2
-1855
1
1750-1815
1
1752-1818
1
1815-1875
1
1818-1861
1
1830-1902
1
1836-1902
1
1854-1861
1
1867-1957
1
1867-1959
1
1870-1945
1
1877-1964
1
18th century
1
1901-1988
1
1904-1977
1
1929
1
1929-2007
1
1933-1945
1
1945-1953
1
1945-1989
1
1951-
1
21st century
1
Cretaceous
1
Devonian
1
Jurassic
1
Mesozoic
1
Paleozoic
1
Permian
1
Quaternary
1
Tertiary
1