New York’s Catskill Mountains name has been the subject of puns. “Catskill ice” was sold in New York City, but it was reported in 1855 that the letter “M” was being written on the ice carts, making it “Catskill mice.” The “Catskill Mountains? Don’t cats kill mice?” joke is still told.
 
   
Wikipedia: Catskill Mountains
The Catskill Mountains, also known as the Catskills, are a large area in the southeastern portion of the U.S. state of New York. They are located approximately 100 miles (160 km) north-northwest of New York City and 40 miles (60 km) southwest of Albany, starting just west of the Hudson River. The Catskills occupy much or all of five counties (Delaware, Greene, Schoharie, Sullivan, and Ulster), with some areas falling into the boundaries of southwestern Albany, eastern Broome, northwestern Orange, and southern Otsego counties. Foothills are also found in southeastern Chenango, southern Montgomery, northern Otsego, and western Schenectady counties. As a cultural and geographic region, the Catskills are generally defined as those areas close to or within the borders of the Catskill Park, a 700,000-acre (2,800 km2) forest preserve protected from many forms of development under New York state law.
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The name Catskills did not come into wide popular use for the mountains until the mid-19th century – in fact, that name was disparaged by purists as too plebeian, too reminiscent of the area’s Dutch colonial past, especially since it was used by the local farming population. It may also have been a continuation of the British practice, after taking possession of the colony in the late 17th century, of trying to replace most Dutch Knickerbocker toponyms in present-day New York with their English alternatives. The locals preferred to call the range the Blue Mountains, to harmonize with Vermont’s Green Mountains and New Hampshire’s White Mountains. It was only after Washington Irving’s stories that Catskills won out over Blue Mountains and several other competitors.
 
Chronicling America
27 June 1855, The Raftsman’s Journal (Clearfield, PA), pg. 4, col. 2:
A wag in New York, standing on the corner at Oliver and Cherry streets, opposite to one of the “Catskill ice” carts, drew a piece of chalk from his pocket and marked M. before the word “ice” which of course made it read “Cats kill mice.”
 
Chronicling America
3 September 1868, The Jeffersonian (Stroudsburg, PA), pg. 1, col. 3:
“Sambo, did you ever see the Catskill mountains?” “No, Clem: but I’ve seen cats kill mice.”
 
30 September 1868, Vermont Watchman and State Journal (Montpelier, VT), “News Items,” pg. 3, col. 2:
“Sambo, did you ever see the Catskill mountains?” “No, Clem: but I’ve seen cats kill mice.”
 
Google Books
September 1889, Manford’s New Monthly Magazine, pg. 560:
“SAMBO, did you ever see the Catskill mountains?” “No, Clem, but I’ve seen cats kill mice.”
 
Chronicling America
24 October 1912, Baxter SPrings (KS) News, “Corner for the Juniors,” pg. 3, col. 1:
Lola Was Skeptical.
“I saw the Catskill mountains last summer,” said small Sadie, who was inclined to boast of her travels. “Did you ever see them?”
 
“No,” replied little Lola, “and I don’t believe they can, either. But I’ve seen cats kill mice.”
   
Google Books
I Wish I’d Said That!:
Being a Discussion of the Art of Repartee by Two Good Listeners, Jack Goodman and Albert Rice
By Jack Goodman and Albert Rice
New York, NY: Simon and Schuster
1935
Pg. 67:
This is the effort of an unknown, in 1898:
 
“Julius,” one of his characters remarks, “have you ever seen the Catskill Mountains?”
“No, John,” came the rejoinder quick as a flash, “but I’ve seen cats kill mice!”
   
Google Books
November 1991, Boys’ Life, “Think & Grin,” pg. 74, col. 1:
Teacher: Ed, have you ever seen the Catskill Mountains?
Ed: No, but I’ve seen cats kill mice.
—Bradley Stone, Buffalo Grove, Ill.
 
Twitter
cjkc ❤️
‏@sophie_li_x
Haha! This is a joke - has anyone ever seen the Catskill Mountains?
No but I’ve seen the cats kill mice!
5:45 AM - 30 Dec 2013