“What bus sailed the ocean?”/“Colum-bus.”

A Christopher Columbus pun is:
   
Q: What bus sailed the ocean?
A: Colum-bus.
 
The riddle has been cited in print since at least 1950.
 
   
Wikipedia: Christopher Columbus
Christopher Columbus (Italian: Cristoforo Colombo; c. 1451 – 20 May 1506) was an Italian explorer, navigator, and colonizer. A citizen of the Republic of Genoa, under the auspices of the Catholic Monarchs of Spain he completed four voyages across the Atlantic Ocean. Those voyages and his efforts to establish permanent settlements on the island of Hispaniola initiated the European colonization of the New World.
 
8 October 1950, Illinois State Register-Journal (Springfield, IL), pg. 8, col. 5:
Riddle: What bus sailed the ocean?
Ans.: Columbus.
—Zita Todi, Raymond.
 
16 August 1956, The Gazette and Daily (York, PA), “Riddles” by Wee Wisom, pg. 33, col. 2:
What bus sailed the ocean?
Columbus.
 
8 August 1971, Boston (MA) Herald Traveler, “Riddles,” Young Folks Page, col. 5:
What bus sailed on the ocean?
From MICHAEL CRITTENDEN
No. Andover
     
18 December 1996, The Sun (London, UK), pg. 8:
What bus sailed the ocean? Colum-bus!
 
Twitter
Bill Helton‏
@7colonel7
Corny joke…What bus sailed the ocean blue?  Columbus!
9:46 AM - 17 Aug 2010
 
Twitter
🐉‏
@Supreme_Chann
What bus sailed across the ocean? ColumBUS. Lolol #LaffyTaffyJokes
1:34 PM - 31 Oct 2012
 
Twitter
ASUCD Unitrans‏
@ASUCDUnitrans
What bus sailed across the Atlantic Ocean? ColumBUS! ... #busjokes #terriblepuns
1:34 PM - 21 May 2014