Era
Precambrian
8
Cretaceous
5
Jurassic
4
Triassic
4
20th century
3
Miocene
3
17th century
2
21st century
2
Eocene
2
Ordovician
2
Paleozoic
2
Pennsylvanian
2
Pliocene
2
-1536
1
-30 B.C.
1
1412-1431
1
1548?-1601?
1
1840-1926
1
1842-1900
1
1871-1944
1
1886-1931
1
1892-1940
1
18th century
1
1904-1980
1
1908-2007
1
1945-
1
1948-
1
1949-
1
1960-2021
1
83 B.C.?-30 B.C.
1
Cambrian
1
Cenozoic
1
Civil War, 43-31 B.C.
1
Mesozoic
1
Mississippian
1
Neogene
1
Oligocene
1
Paleocene
1
Permian
1
Pleistocene
1
Revolution, 1775-1783
1
Tertiary
1
To 1763
1