Above, a 1934 plaque from the Big Apple Night Club at West 135th Street and Seventh Avenue in Harlem. Discarded as trash in 2006. Now a Popeyes fast food restaurant on Google Maps.

Entry from October 20, 2021
“What’s the difference between one yard and two yards?"/"A fence.”

"Yard” can mean a unit of length equal to three feet, and it can also mean the property surrounding one’s house. A riddle is:

Q: What’s the difference between one yard and two yards?
A: A fence.

The joke has been cited in print since at least 1878.

Newspapers.com
22 February 1878, The Star of Pascagoula (Pascagoula, MS), “Funnygraphs,” pg. 4, col. 3:
Teacher—“What is the difference between one yard and two yards?” “A fence,” replied Tommy Blazes, and then Tommy sat down fourteen times on a ruler.

Newspapers.com
7 March 1878, Murfreesboro (NC) Enquirer, pg. 3, col. 2:
‘What is the difference between one yard and two yards?’ asked the teacher in arithmetic. ‘A fence,’ said Tommy Beals. Then Tommy sat down on the ruler fourteen times.

February 1880, St. Nicholas magazine, pg. 359:
RIDDLE.
What is the difference between one yard and two yards?

Conundrums, Riddles and Puzzles:
Containing One Thousand of the Latest and best Conundrums gathered from every conceivable source

By Dean Rivers
Philadelphia, PA; The Penn Publishing Company
1910
Pg. 54:
What is the difference between one yard and two yards? A fence.

The Stay-at-Home Book for Boys and Girls
By Robert Cleveland
New York, NY: Greenberg
1944
Pg. 88:
What is the difference between one yard and two yards? A fence.

Complete Speaker’s and Toastmaster’s Library
By Jacob M. Braude
Englewood Cliffs, NJ: Prentice-Hall
1965
Pg. 29:
Fence: the difference between one yard and two yards.

Free homepages . . . ..
Ragga
Aug 19, 1996, 3:00:00 AM
(...)
... Fence: The difference between one yard and two yards. . . . . . . .--- Blue Wave/QWK v2.10

Playing with Conundrums
Carl G.
Jan 21, 2000, 3:00:00 AM
(...)
5. What is the difference between one yard and two yards?
Usually a fence.

“Puns of the Weak” 7/14/00
Stan Kegel
Jul 15, 2000, 3:00:00 AM
(...)
What is the difference between one yard and two yards? A fence (Syman Hirsch)

Paul
@forces2
What’s the difference between one yard and two yards? A fence
2:45 AM · Jun 21, 2009·Twitter Web Client

Annoying Orange
@annoyingorange
HEY! What’s the difference between one yard and two yards? A fence! HAHAHA!
2:04 PM · Feb 9, 2012·TweetDeck

Conundrums, Riddles and Puzzles
By Dean Rivers
Good Press
2021
Pg. ?:
What is the difference between one yard and two yards? A fence.

Reddit—Cleanjokes
Posted by u/SheldonE65 October 21, 2021
What is the difference between one yard and two yards?
A fence