A popular baseball riddle is:
 
Q. What runs around a baseball field, but never moves?
A. A fence.

The joke has been cited in print since at least 1990. However, this wasn’t originally a riddle about a baseball field. “What runs all around a pasture, but never moves?” was cited in print in 1957. “What runs all around the yard, but never moves?” was cited in 1973. “What runs around a field, but never moves?” was cited in 1979.
 
 
8 October 1957, St. Louis Daily Livestock Reporter (East St. Louis, IL), “For Juniors,” pg. 4, col. 4:
What runs all around a pasture but never moves? The fence.
 
Google News Archive
3 July 1972, The Free Lance-Star (Fredericksburg, VA),  “Fun Time—Riddle Box,“pg. 20, col. 2:
What runs around the yard and always stands still?
A fence.
 
27 August 1973, Dunkirk Evening Observer (Dunkirk-Fredonia, NY), “Mini Jokes,” pg. 18, col. 1:
Q. What runs all around the yard but never moves?
A. Fence!
 
Google Books
What’s to Eat?: And Other Questions Kids Ask about Food
U.S. Department of Agriculture
Washington, DC: Government Printing Office
1979
Pg. 53:
Sue: What runs around a field, but never moves?
Lou: A fence.
 
1 July 1990, Cedar Rapids (IA) Gazette, “Send Me a Riddle,” comics page:
Q. WHAT RUNS AROUND A BASEBALL FIELD BUT NEVER MOVES?
A. A FENCE.
JESSICA CORSI, PALMER, MA
 
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Baseball Field - What goes all the way around a baseball field but never moves?

The fence http://godark.us/tu164926
2:00 AM - 17 Sep 2009
 
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What goes all the way around a baseball field but never moves? The fence
5:10 PM - 17 Apr 2015