Era
1854-1861
38
Pennsylvanian
26
Civil War, 1861-1865
16
Cretaceous
16
19th century
10
Permian
10
Precambrian
10
20th century
9
1837-1865
6
Carboniferous
5
Paleozoic
5
1865-1950
3
1870-1945
3
Ordovician
3
Pleistocene
3
Quaternary
3
1800-1859
2
1814-1866
2
1853-1857
2
1867-1924
2
1916-1951
2
1924-1984
2
1928-1965
2
1931-1965
2
1951-
2
Cenozoic
2
Devonian
2
Jurassic
2
Mesozoic
2
Tertiary
2
1775-1865
1
1789-1869
1
1803-1885
1
1809-1867
1
1817-
1
1819-1873
1
1836-1902
1
1836-1910
1
1841-1900
1
1842-1913
1
1844-1917
1
1848-1929
1
1851-1911
1
1856-
1
1859-1925
1
1860-1936
1
1861-1865
1
1870-1946
1
1871-1954
1
1877-
1
more ...