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.” This region was also called the “Jewish Alps” or the “Yiddish Alps,” located in “Solomon County” (a nickname of Sullivan County). Another nickname for this region is the “Sour Cream Alps.”
           
“The Lambs and Friars Clubs (both theatrical orgs) will battle it out in a three-day war of golf at the Concord in the Sour Cream Alps” was printed in the Evening Herald (Shenandoah, PA) on July 18, 1966. “THE CONCORD Hotel in the Sour Cream Alps signed Liberace” was printed in the Asbury Park (NJ) Evening Press on June 21, 1967. “The huge famed Concord resort in the sour cream Alps (the Catskills)” was printed in the Evening Herald and Ashland Daily News (Shenandoah, PA) on September 27, 1967. All of the early citations are from the syndicated “Voice of Broadway” column by Jack O’Brian (1914-2000), who probably coined the term.
   
 
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”.
     
Wikipedia: Jack O’Brian     
John Dennis Patrick O’Brian (August 16, 1914 – November 5, 2000) was an entertainment journalist best known for his longtime role as a television critic for New York Journal American
(...)
After the death of Dorothy Kilgallen, his colleague at the Journal American, in November 1965, O’Brian took over her old Voice of Broadway column.
 
Newspapers.com
18 July 1966, Evening Herald (Shenandoah, PA), “Voice of Broadway” by Jack O’Brian, pg. 6, col. 7:
The Lambs and Friars Clubs (both theatrical orgs) will battle it out in a three-day war of golf at the Concord in the Sour Cream Alps.
     
Newspapers.com
23 July 1966, Pottstown (PA) Mercury, “Voice of Broadway” by Jack O’Brian, pg. 4, col. 2:
The Lambs and Friars Clubs (both theatrical orgs) will battle it out in a three-day war of golf at the Concord in the Sour Cream Alps.
 
Newspapers.com
21 June 1967, Asbury Park (NJ) Evening Press, “Voice of Broadway” by Jack O’Brian, pg. 30, col. 5:
THE CONCORD Hotel in the Sour Cream Alps signed Liberace, ...
 
Newspapers.com
27 September 1967, Evening Herald and Ashland Daily News (Shenandoah, PA), “The Voice of Broadway” by Jack O’Brian, pg. 6, col. 3:
The huge famed Concord resort in the sour cream Alps (the Catskills) sent its booker Phil Greenwald to London to try to sign Israeli star Topol; ...
 
Newspapers.com
31 January 1968, Vineland (NJ) Times Journal,  “Voice of Broadway” by Jack O’Brian, pg. 20, col. 4:
Maybe Farah should pack mom off to a Singles Weekend at Grossinger’s of The Concord in the Sour Cream Alps.
 
CSI Today
SEPTEMBER 17, 2015 BY TERRY MARES
The Catskills: Its History and How It Changed America
(...)
The Catskills were this nation’s original frontier, northwest of New York City and its first great vacationland–an almost godlike majesty of mountains and landscapes, skies, waterfalls, pastures, and cliffs. The Catskills were a refuge and home to poets and gangsters, tycoons and politicians, preachers and outlaws, musicians and spiritualists, outcasts and rebels, and the resorts that after World War II catered to upwardly mobile Jewish families, giving rise to hundreds of hotels inspired by Grossinger’s, the original “Disneyland with knishes”—the Concord, Brown’s Hotel, Kutsher’s Hotel, and others—in what became known as the Borscht Belt and Sour Cream Alps.
 
The Times of Israel—Sheldon Kirshner blog
The Bygone Era of the Jewish Catskills Resorts
SEP 25, 2018, 9:43 PM
(...)
Jews began flocking in droves to the Catskills in the early 20th century, greatly accelerating its growth. Grossinger’s, one of the the first major hotels to cater to a Jewish clientele, competed with the Concord, Brown’s, Kutscher’s and the Nevele, among others. With the passage of time, the Catskills became known as the Borscht Belt and the Sour Cream Alps.