Era
20th century
171
19th century
153
Civil War, 1861-1865
147
1866-1895
128
Colonial period, ca. 1600-1775
93
18th century
50
1934-
42
1980-
42
21st century
37
1948-1980
31
17th century
30
1979-
29
1982-
29
1815-1875
28
1862-1865
27
Cretaceous
25
Revolution, 1775-1783
25
1869-1934
24
1789-1869
23
To 1848
21
Tertiary
19
1839-1876
18
Wars of Independence, 1806-1830
18
16th century
16
1945-
16
Mesozoic
16
Paleozoic
16
Pleistocene
15
To 1830
14
1829-1890
13
1834-1902
13
To 1803
13
Cenozoic
12
To 1775
12
To 1810
12
To 1789
11
To 1846
11
1750-1815
10
1783-1830
10
1808-1889
10
1945-1982
10
1775-1783
9
1775-1865
9
1783-1865
9
1848-1860
9
Devonian
9
Precambrian
9
Triassic
9
1807-1870
8
1933-1945
8
more ...