In case you ever wondered why a large number of your ancestors disappeared during a certain period in history, this might help. Epidemics have always had a great influence on people - and thus influencing as well, the genealogists trying to trace them. Many cases of people disappearing from records can be traced to their dying during an epidemic or moving away from the affected area. Some of the major epidemics in the United States are listed below:

Year	Location	Disease
1657	Boston, Massachusetts	Measles
1687	Boston, Massachusetts	Measles
1690	New York, New York	Yellow Fever
1713	Boston, Massachusetts	Measles
1729	Boston, Massachusetts	Measles
1732-3	Worldwide	Influenza
1738	South Carolina	Smallpox
1739-40	Boston, Massachuetts	Measles
1747	Connecticut, New York, Pennsylvania, South Carolina	Measles
1759	North America (occupied by non-Native Americans)	Measles
1761	North America and West Indies	Influenza
1772	North America	Measles
1775	North America (especially New England)	Unknown
1775-6	Worldwide (one of worst epidemics)	Influenza
1783	Dover, Delaware (high fatalities)	Bilious Disorder
1788	Philadelphia, Pennsylvania, and New York, New York	Measles
1793	Vermont (putrid fever)	Influenza; Fever
1793	Virginia (killed 500 in 5 counties in 4 weeks)	Influezna
1793	Philadelphia, Pennsylvania (one of the worst)	Yellow Fever
1793	Harrisburg, Pennsylvania	Unknown
1793	Middletown, Pennsylvania	Unknown
1794	Philadelphia, Pennsylvania	Yellow Fever
1796-7	Philadelphia, Pennsylvania	Yellow Fever
1798	Philadelphia, Pennsylvania (one of the worst)	Yellow Fever
1803	New York	Yellow Fever
1820-3	United States (Started in Schuylkill River area)	Fever
1831-2	United States (brought by English immigrants)	Asiatic Cholera
1832	New York City and other major cities	Cholera
1833	Columbus, Ohio	Cholera
1834	New York, New York	Cholera
1837	Philadelphia, Pennsylvania	Typhus
1841	United States, especially in the South	Yellow Fever
1847	New Orleans, Louisana	Yellow Fever
1847-8	Worldwide	Influenza
1848-9	North America	Cholera
1849	New York, New York	Cholera
1850	United States	Yellow Fever
1850-1	North America	Influenza
1851	Coles Co., Illinois; Great Plains; Missouri	Cholera
1852	United States (8,000 died in New Orleans that summer)	Yellow Fever
1855	United States	Yellow Fever
1857-9	Worldwide (major outbreak)	Influenza
1860-1	Pennsylvania	Smallpox
1865-73	Philadelphia, Pennsylvania; New York, New York, Boston, Massachusetts; and New Orleans, Louisana	Smallpox
	Baltimore, Maryland; Memphis, Tennessee; Washington, D.C. (also Typhus, Typhoid, Scarlet Fever, and Yellow Fever)	Cholera
1873-5	North America and Europe	Influenza
1878	New Orleans, Louisiana	Yellow Fever
1885	Plymouth, Pennsylvania	Typhoid
1886	Jacksonville, Florida	Yellow Fever
1918	Worldwide (major outbreak)	Influenza