Era
20th century
10,906
19th century
5,185
21st century
2,732
18th century
1,583
1564-1616
1,018
Civil War, 1861-1865
991
17th century
973
1945-
892
Cretaceous
838
1945-1989
748
16th century
591
1933-1945
553
Revolution, 1775-1783
519
1946-
492
1989-
484
Tertiary
447
To 1500
441
Quaternary
417
2009-
408
2001-2009
389
Early modern, 1500-1700
385
Colonial period, ca. 1600-1775
372
1991-
349
Precambrian
346
Paleozoic
334
Cenozoic
293
1960-
279
1951-
273
2000-
261
1929
252
Permian
250
1809-1865
239
Eocene
235
1918-1945
228
Jurassic
225
1993-2001
223
1981-2001
217
Mesozoic
216
1949-
210
Pennsylvanian
206
Miocene
201
1947-
195
Pleistocene
193
1948-
192
1961-1970
189
Ordovician
189
Devonian
174
1991-2000
172
1979-
171
1945-1953
168
more ...