Period 1: 1491-1607
Period 2: 1607-1754
Period 3: 1754-1800
Period 4: 1800-1848
Period 5: 1844-1877
Period 6: 1865 - 1898
Period 7: 1890 - 1945
Period 8: 1945-1980
Period 9: 1980-Present