Jewish entertainers, in the period of about 1920 to 1970, frequently performed at hotels in the Catskill Mountains in New York that were dubbed the “borscht belt” or “borscht circuit.” Borscht is a popular food that these Jewish entertainers (usually from Eastern European families) often ate.
       
“Borsht circuit” was printed in Variety (New York, NY) on May 1, 1935. “Borscht belt” was printed in Variety on June 2, 1937. “Variety calls the up-state summer hotel cabarets ‘The Bortsch Circuit’” was printed in O. O. McIntyre’s syndicated “New York Day by Day” column on July 22, 1937.
       
The Borscht Belt/Circuit has also been called the “Jewish Alps,” “Yiddish Alps” and “Sour Cream Alps.”
 
   
Wikipedia: Borscht Belt
Borscht Belt, or Jewish Alps, is a nickname for the (now mostly defunct) summer resorts of the Catskill Mountains in parts of Sullivan, Orange, and Ulster counties in New York. Borscht, a soup associated with immigrants from eastern Europe, was a metonym for “Jewish”. These resorts were a popular vacation spot for New York City Jews between the 1920s and the 1970s. Most Borscht Belt resorts hosted traveling Jewish comedians and musicians, and many who later became prominent began their careers there.
 
The tradition of Borscht Belt entertainment began in the early twentieth century with the indoor and outdoor theaters constructed on a 40-acre (16-hectare) tract in Hunter, New York, by Yiddish theater star Boris Thomashefsky.
 
Beginning in the 1980s, the growth of air travel made the Catskills less attractive, so many of the resorts eventually closed, although Jewish culture has remained present.
(...)
Some of the Catskill hotels were converted from farms that immigrant Jews had started in the early 1900s. As the area grew, it began to cater specifically to Jews, providing kosher food, synagogues, and other features of Jewish communities, including entertainment. The area became known as “The Jewish Alps”, and the Sullivan County portion as “Solomon County”.
   
(Oxford English Dictionary)
borscht belt, n. and adj.
Etymology: < borscht, variant (after Yiddish borsht) of borsch n. + belt n.1 Compare earlier borscht circuit n. and adj.
U.S. colloquial.
The hotels of) a resort area in the Catskill Mountains, New York State, popular with Jewish people of Eastern European origin; these hotels as a source of (esp. summer) engagements for an entertainer or show.
1937   Variety 2 June 47   The injection of class into the borscht belt’s entertainment end.
1940   Gettysburg (Pa.) Times 18 July 3/2   The Broadway borscht belt will sprout a dude ranch.
1946   J. Adams From Gags to Riches iii. 48   For me, and for a lot of other actors, the borsht belt, in the Catskill Mountains, was a lifesaver during the summer months.
 
borscht circuit, n. and adj.
Etymology: <

borscht, variant (after Yiddish borsht) of borsch n. + circuit n. Compare borscht belt n.
U.S. colloquial.
The hotels of resort areas in the Catskill Mountains, New York State, as a source of (esp. summer) engagements for an entertainer or show.
The area itself later became known informally as the borscht belt: see borscht belt n.
1936   Variety 29 July 1/5   Mountain hotels on the borscht circuit are instructing their agents to discontinue sending single women or mixed couples.
1940   S. Lewis Bethel Merriday 165   I’ve been out on the Borscht circuit all summer.
         
1 May 1935, Variety (New York, NY), “Broadway,” pg. 53, col. 1:
Sign of summer: resort ‘social directors’ clogging up 46th street curb waiting for open spots on the borsht circuit.
 
Newspapers.com
8 August 1936, The Morning Chronicle (Manhattan, KS), “New Yorker at Large” by Jack Stinnett, pg. 4, col. 3:
‘Mixing a Must, Mixed Teams a Bust—‘Life on the Borscht Circuit’
“Not satisfied with the entertainment they have, mountain hotels on the borscht circuit are instructing their agents (booking entertainment acts) to discontinue sending single women or mixed couples.”
   
Newspapers.com
10 May 1937, The Daily Record (Long Branch, NJ), “In New York” by George Ross, pg. 6, col. 4:
For seven summer,s he earned his bread and butter on what is popularly known as the “Borsch Circuit,” which consists of those innumerable adult camps in the Catskills and Adirondacks. 
   
Newspapers.com
22 July 1937, The Daily Messenger (Madisonville, KY), “New York Day by Day” by O. O. McIntyre, pg. 4, col. 2:
Variety calls the up-state summer hotel cabarets “The Bortsch Circuit.”
 
12 January 1938, Daily News (New York, NY), “Broadway” by Dan Walker, pg. 42, col. 1:
Max Gordon is going on the borsht circuit!
   
Google Books
31 January 1938, Life (New York, NY), pg. 39:
An early admirer of “Bei Mir” was Mrs. Jeannie Grossinger, of Grossinger Hotel, Ferndale, N.Y. The Grossinger Hotel is on the fringe of the Catskills, known as the “Yiddish alps” or the “borscht belt.”
 
Newspapers.com
12 March 1938, Saskatoon (Saskatchewan) Star-Phoenix, “Happy Singers,” The Prairie Pals sec., pg. 4, col. 3:
An early admirer of “Bei Mir” was Mrs. Jeannie Grossinger, of Grossinger Hotel, Ferndale, N.Y. The Grossinger Hotel is on the fringe of the Catskills, known as the “Yiddish alps” or the “borscht belt.”
 
OCLC WorldCat record
The Borscht Belt,
Author: Joey Adams; Henry Tobias
Publisher: New York, Bentley Pub. Co. [1973]
 
OCLC WorldCat record
Rise and fall of the Borscht Belt.
Author: Peter Davis; Joseph Wiseman; Villon Films.
Publisher: Hurleyville, NY : Villon Films, ©1985.
Edition/Format:   Film : Film   Visual material : English
Summary:
Documents the development of the resort community known as the “borscht belt” in the Catskill Mountains of New York. Jewish farmers settling in the area at the turn of the century, took in summer boarders to supplement their meager farm incomes. In a short time, tourism was the major industry with more than a million Jews vacationing at farms, guest houses, and elegant resort hotels. The program describes reasons for the region’s popularity and explains factors that led to its decline in the early 1960
Edition/Format:   Print book : Biography : English
 
OCLC WorldCat record
The Borscht Belt : revisiting the remains of America’s Jewish vacationland
Author: Marisa Scheinfeld; Stefan Kanfer; Jenna Weissman Joselit
Publisher: Ithaca : Cornell University Press, 2016.
Edition/Format:   Print book : English
Summary:
Today ‘the Borscht Belt’ is recalled through the nostalgic lens of summer swims, Saturday night dances, and comedy performances. But its current state, like that of many other formerly glorious regions, is nothing like its earlier status. Forgotten about and exhausted, much of its structural environment has been left to decay. ‘The Borscht Belt’, which features essays by Stefan Kanfer and Jenna Weissman Joselit, presents Marisa Scheinfeld’s photographs of abandoned sites where resorts, hotels, and bungalow colonies once boomed in the Catskill Mountain region of upstate New York. The book assembles images Scheinfeld has shot inside and outside locations that once buzzed with life as year-round havens for generations of people. Some of the structures have been lying abandoned for periods ranging from four to twenty years, depending on the specific hotel or bungalow colony and the conditions under which it closed. Other sites have since been demolished or repurposed, making this book an even more significant documentation of a pivotal era in American Jewish history. “The Borscht Belt’ presents a contemporary view of more than forty hotel and bungalow sites. From entire expanses of abandoned properties to small lots containing drained swimming pools, the remains of ‘the Borscht Belt’ era now lie forgotten, overgrown, and vacant. In the absence of human activity, nature has reclaimed the sites, having encroached upon or completely overtaken them. Many of the interiors have been vandalized or marked by paintball players and graffiti artists. Each ruin lies radically altered by the elements and effects of time. Scheinfeld’s images record all of these developments