"I received this on another list - very informative!  But always in the case of someone else's research - you need to check out these dates to your own satisfaction." 

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:

1657    Boston Measles
1687    Boston Measles
1690    New York Yellow Fever
1713    Boston Measles
1729    Boston Measles
1732-3  Worldwide Influenza
1738    South Carolina Smallpox
1739-40 Boston Measles
1747    CT,NY,PA,SC Measles
1759    N. America [areas inhabited by white people] Measles
1761    North America and West Indies Influenza
1772    North America Measles
1775    N. America [especially hard in NE] epidemic       Unknown
1775-6  Worldwide [one of the worst epidemics] Influenza
1783    Dover, DE ["extremely fatal"]    Bilious Disorder
1788    Philadelphia and New York Measles
1793    Vermont [a "putrid" fever] and Influenza
1793    VA [killed 500 in 5 counties in 4 weeks]       Influenza
1793    Philadelphia [one of the worst epidemics]      Yellow Fever
1793    Harrisburg, PA [many unexplained deaths]       Unknown
1793    Middletown, PA [many mysterious deaths] Unknown
1794    Philadelphia, PA Yellow Fever
1796-7  Philadelphia, PA Yellow Fever
1798    Philadelphia, PA [one of the worst] Yellow Fever
1803    New York Yellow Fever
1820-3  Nationwide [starts Schuylkill River and spreads] "Fever"
1831-2  Nationwide [brought by English emigrants] Asiatic Cholera
1832    NY City and other major cities Cholera
1837    Philadelphia Typhus
1841    Nationwide [especially severe in the south] Yellow Fever
1847    New Orleans Yellow Fever
1847-8  Worldwide Influenza
1848-9  North America Cholera
1850    Nationwide Yellow Fever
1850-1  North America Influenza
1852    Nationwide [New Orleans-8,000 die in summer]   Yellow Fever
1855    Nationwide [many parts] Yellow Fever
1857-9  Worldwide [one of the greatest epidemics]       Influenza
1860-1  Pennsylvania Smallpox
1865-73 Philadelphia, NY, Boston, New Orleans} {Smallpox
Baltimore, Memphis, Washington DC} Cholera and a series of recurring epidemics of:
Typhus, Typhoid, Scarlet Fever, Yellow Fever

1873-5  North America and Europe Influenza
1878    New Orleans [last great epidemic] Yellow Fever
1885    Plymouth, PA Typhoid
1886    Jacksonville, FL Yellow Fever
1918    (high point year) Influenza   Worldwide more people were hospitalized in WWI from this epidemic than  wounds.  US Army training   camps became death  camps, with 80% death rate in some camps. 

Finally, these specific instances of cholera were mentioned:

1833    Columbus, OH
1834    New York City
1849    New York
1851    Coles Co., IL, The Great Plains, and Missouri