Era
20th century
12
Cession to the United States, 1819
5
Paleozoic
5
Quaternary
5
Tertiary
5
To 1821
5
Huguenot colony, 1562-1565
4
Pliocene
4
Spanish colony, 1565-1763
4
approximately 1500-1542
4
18th century
3
1946-
3
21st century
3
Colonial period, ca. 1600-1775
3
Miocene
3
To 1803
3
1767-1845
2
1896-1953
2
1929
2
1948-
2
1951-
2
1959-1990
2
19th century
2
2000
2
Civil War, 1861-1865
2
Cretaceous
2
Devonian
2
Holocene
2
Neogene
2
Silurian
2
Spanish colony, 1784-1821
2
To 1565
2
1510-1554
1
1519-1574
1
1533?-1588
1
1585-1590
1
1739-1812
1
1751-1836
1
1767-1848
1
1821-1865
1
1829-1909
1
1853-1895
1
1857-1910
1
1870-1938
1
1871-1938
1
1882-1945
1
1907-1990
1
1908-1993
1
1913-2004
1
1922-1987
1
more ...