Era
20th century
10,933
19th century
5,196
21st century
2,751
18th century
1,580
1564-1616
1,021
Civil War, 1861-1865
991
17th century
975
1945-
894
Cretaceous
838
1945-1989
751
16th century
592
1933-1945
554
Revolution, 1775-1783
519
1946-
496
1989-
485
Tertiary
447
To 1500
441
Quaternary
417
2009-
408
2001-2009
389
Early modern, 1500-1700
386
Colonial period, ca. 1600-1775
373
1991-
351
Precambrian
346
Paleozoic
335
Cenozoic
294
1960-
281
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-
196
Pleistocene
194
1948-
192
Ordovician
190
1961-1970
189
Devonian
174
1991-2000
172
1979-
171
1945-1953
169
more ...