Era
Cretaceous
114
Quaternary
92
Paleozoic
33
Precambrian
33
Cenozoic
26
Tertiary
23
Jurassic
20
Mesozoic
18
Civil War, 1861-1865
17
Pre-Quaternary
15
Eocene
14
Permian
13
Pennsylvanian
12
20th century
10
Cambrian
8
19th century
7
Paleocene
7
Ordovician
6
Pleistocene
6
Proterozoic
6
Partition, 1995
5
Revolution, 1775-1783
5
Devonian
3
Holocene
3
Miocene
3
Mississippian
3
Neogene
3
Paleogene
3
Triassic
3
1831-1897
2
1866-1895
2
1945-
2
1979
2
1979-
2
21st century
2
Oligocene
2
To 146 B.C.
2
1200-1259
1
1254-1323?
1
1470-1519
1
1485-1547
1
1596-1673
1
1728-1801
1
1729-1824
1
1735-1809
1
1770-1838
1
1774-1809
1
1781-1870
1
17th century
1
1810-1873
1
more ...