Longest continuous joke-telling session by a comedian:

101 hours and 39 minutes
In February 1993, British comic John Martin set the world record for longest joke-telling session by doing standup for 101 hours and 39 minutes at the Crown Hotel in Liverpool, England.
Source: Guardian Unlimited, 7/22/2010

 
   
 
Christy Tidwell (flickr 2008)
Record for most jokes told in an hour:

549
According to the Guinness Book of World Records, in May 2005, Anthony Lehmann told a record 549 jokes in one hour at the Rhino Room in Adelaide, Australia.
Source: Sunday Telegraph (Australia), 9/21/2008

 
   
 
Knickerbocker (March 1847)
Earliest known "Why did the chicken cross the road?" joke:

March 1847
According to Smithsonian Magazine, the first "Why did the chicken cross the road joke" to appear in print was in the March 1847 issue of the Knickerbocker, or New York Monthly, magazine. The magazine wrote: "Why does a chicken cross a street? Are you out of town? Do you give it up? Because it wants to get on the other side!"
Source: Smithsonian, 2/1/2008

 
   
  First joke book in English is published:

1484
In 1484, William Caxton, the first English printer of books, included some of Poggio Bracciolini's jokes from the Liber Facetiarum in a translation of Aesop's Fables in what was the first joke book in the English language.
Source: Stop Me If You've Heard This, Holt,