“Why did the chicken cross the road?”/“To get to the other side” is a classic riddle from the 19th century. A playground variation is:
 
Q: Why did the chicken cross the playground?
A: To get to the other slide.
 
The joke was printed in many newspapers in January 1985.
 
   
20 January 1985, Arkansas Democrat (Little Rock, AR), “Humor Takes Its Toll,” Family Weekly, pg. 15, col. 1:
Why did the chicken cross the playground?
TO get to the other slide.
 
Google Books
September 1988, Boys’ Life “Think & Grin,” pg. 64, col. 2:
Tiger: Say, Woody, why did the chicken cross the playground?
Webelos Woody: You got me. Why?
Tiger: To get to the other slide! — Emma Black, Birmingham, Ala.
 
11 February 1990, Chicago (IL) Tribune, “Got It?,” Spots (comic sec.), pg. 1, col. 2:
Q. Why did the chicken cross the playground?
A. To get to the other slide.
Bridget Nicholson, 8, Barrington
 
5 October 1990, Milwaukee (WI) Sentinel, “There’s a reason for all the honking when geese are overheard” by Alex Thien, sec. 3, pg. 1:
Q: Why did the chicken cross the playground?
A: To get to the other slide.
 
Google Books
Kids’ Funniest Jokes
Edited by Sheila Anne Barry
Illustrated by Jeff Sinclair
New York, NY: Sterling Publishing Company, Inc.
1993
Pg. 81:
Why did the chicken cross the playground?
To get to the other slide. JOHN ROY, 12
   
Google Groups: rec.humor
Canonical List of Chicken/Road Crossing Jokes ver 0.1
Thomas Parker
1/30/94
(...)
Q:  Why did the chicken cross the playground?
A:  To get to the other slide!!!!
 
Google Books
Penguin Pocket Jokes
By David Pickering
New York, NY: Penguin Books
2006
Pg. ?:
Why did the chicken cross the playground?
To get to the other slide.
 
Twitter
James
‏@crossmage
@debutaunt Why did the chicken cross the playground?  Why, to get to the other Slide, of course…
10:56 PM - 28 Jul 2008
 
Google Books
Jokelopedia:
The Biggest, Best, Silliest, Dumbest Joke Book Ever!
By Eva Blank, Alison Benjamin, Rosanne Green, Ilana Weitzman and Lisa Sparks
New York, NY: Workman Publishing
2013
Pg. ?:
Why did the chicken cross the playground?
To get to the other slide.
 
Google Books
The Silly Book of Side-Splitting Stuff
By Andy Seed
Illustrated by Scott Garett
London: A & C Black
2014
Pg. 121:
Why did the chicken cross the playground?
To get to the other slide.