Thanksgiving or Thanksgiving Day, currently celebrated on the 
fourth Thursday in November by federal legislation in 1941, has been an 
annual tradition in the United States by presidential proclamation since
 1863 and by state legislation since the 
Founding Fathers of the United States. Historically, Thanksgiving began as a tradition of celebrating the 
harvest of the year.
source: http://en.wikipedia.org/wiki/Thanksgiving
  
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