“New York…when civilization falls apart, remember, we were way ahead of you” is a jocular one-line saying that has been printed on several images. American comedian David Letterman, host of NBC’s late night television comedy show Late Night with David Letterman, made the remark, but it’s uncertain on what show the comment was made.
 
“‘New York… when civilization falls apart, remember, we were way ahead of you.’ - David Letterman” was posted on the newsgroup alt.tv.simpsons on March 1, 1991.
   
   
Wikipedia: David Letterman
David Michael Letterman (born April 12, 1947) is an American former television host, comedian, writer, and producer. He hosted a late night television talk show for 33 years, beginning with the February 1, 1982 debut of Late Night with David Letterman on NBC, and ending with the May 20, 2015 broadcast of Late Show with David Letterman on CBS. In total, Letterman hosted 6,028 episodes of Late Night and Late Show, surpassing friend and mentor Johnny Carson as the longest-serving late night talk show host in American television history. In 1996 Letterman was ranked 45th on TV Guide‘s 50 Greatest TV Stars of All Time.
 
Google Groups: alt.tv.simpsons
Bart Simpson’s Butterfinger Commercial
Steve Baumgarten
3/1/91
(...)
“New York… when civilization falls apart, remember, we were way ahead of you.” - David Letterman
   
Google Groups: rec.games.pinball
HURRICANE hits New York City!
Steve Baumgarten
12/26/91
(...)
“New York… when civilization falls apart, remember, we were way ahead of you.” - David Letterman
 
Google Books
That’s Really Funny:
Over 1,000 More Great Jokes from Today’s Hottest Comedians
Kansas City, MO: Andrews McMeel Publishing, Cader Books
2000
Pg. 174:
New York…When civilization falls apart, remember, we were way ahead of you. -DAVID L6TTERMAN
 
27 December 2005, Chicago (IL) Tribune, “Truth in advertising: New Yorkers (love) the city” by Kirsten Scharnberg, sec. 1, pg. 4, col. 6:
‘New York ... when civilization falls apart, remember, we were way ahead of you.’—David Letterman
 
22 March 2008, Daily Tribune (Wisconsin Rapids, WI), pg. C6, col. 2:
QUOTE OF THE DAY
“New York…when civilization falls apart, remember, we were way ahead of you.”
—David Letterman
 
Twitter
cowsay‏
@cowsay
New York… when civilization falls apart, remember, we were way ahead of you. —David Letterman
2:08 PM - 14 Jun 2008
 
Vulture
150+ Classic Jokes About New York and Los Angeles
By Matthew Love and Ramsey Ess
February 19, 2016 11:07 a.m.
(...)
“New York … when civilization falls apart, remember, we were way ahead of you.” ―David Letterman
 
Twitter
Mike T‏
@miket2598
New York… when civilization falls apart, remember, we were way ahead of you. ― David Letterman
6:45 AM - 20 Mar 2017