Era
20th century
10,760
19th century
4,724
21st century
2,682
18th century
1,496
1564-1616
1,017
Civil War, 1861-1865
989
17th century
943
1945-
884
Cretaceous
837
1945-1989
748
16th century
574
1933-1945
550
Revolution, 1775-1783
519
1946-
492
1989-
484
Tertiary
445
To 1500
429
Quaternary
417
2009-
408
2001-2009
389
Early modern, 1500-1700
385
Colonial period, ca. 1600-1775
372
1991-
350
Precambrian
346
Paleozoic
334
Cenozoic
293
1960-
278
1951-
270
2000-
259
Permian
250
1809-1865
238
Eocene
235
1929
230
1918-1945
227
Jurassic
225
1993-2001
223
Mesozoic
216
1981-2001
213
1949-
208
Pennsylvanian
206
Miocene
201
1947-
196
Pleistocene
194
1948-
191
Ordovician
189
Devonian
174
1979-
171
1945-1953
168
1950-
167
1608-1674
166
more ...