In the early 20th century, New York's lower east side had a denser population than Calcutta does today – there were 500 people per acre, and a widely spreading sense of doom and gloom. As Jews climbed into the middle-class, they escaped the stress of city life to summer in the Catskills. And so began the rich heritage of Borscht Belt Jewish humor in the Catskills.

I just got back from a pleasure trip. I took my mother-in-law to the airport.

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 beet-based soup popular with Ashkenazi Jewish immigrants, was a colloquialism for "Jewish". These resorts were a popular vacation spot for New York City Jews between the 1920s and the 1970s. Beginning in the 1980s the growth of air travel made the Catskills less attractive.

Well known resorts in the area included:

The Well, Concord, Grossinger's, Brickman's, Brown's Hotel, Kutsher's Hotel and Country Club, the Nevele, Friar Tuck Inn, Gibber's, Gilbert's, Granit, the Woodbine Hotel, the Heiden Hotel, Irvington, Lansman's, The Laurels Hotel and Country Club, The Pines Resort, Raleigh, Silverman's River View Hotel, Stevensville, Stiers, the Tamarack Lodge, the Olympic, and the Windsor Regency.

Most Borscht Belt resorts hosted traveling Jewish comedians and musicians, and many who later became famous began their careers there. Their common experience was fodder for Edward Israel Iskowitz, rebranded as Eddie Cantor; Nathan Birnbaum, reborn as George Burns; and Benjamin Kubelsky, who emerged as Jack Benny.

The successful ones moved into the broader American entertainment landscape of network TV, where Danny Kaye (born David Daniel Kaminsky), Sid Caesar and Woody Allen helped America become somewhat less culturally homogenous.

In the 2013 documentary, When Comedy Went to School, filmmakers Mevlut Akkaya and Ron Frank interviewed pioneer stars of the Borscht Belt standup movement in the Catskills, such as Jackie Mason, in this clip.

Between 1930 and 1960, the Borscht Belt resorts offered primarily young men (and some women, notably Molly Picon and Fanny Brice) a ticket into the middle class – and a chance to reinvent themselves without abandoning their roots in vaudeville and Yiddish theater.

People are often brought together when they share common interests or a common culture, but few things bond more strongly than shared pain. In the Catskills, thousands of Jewish people, many of them immigrants, vacationed in summers for a scenic and comic respite from everyday life. The Borscht Belt attracted Jewish families who were excluded from other destinations for many years, particularly during the 1930s. Often displaced, persecuted and excluded, the Catskills became a mecca not only for Jews in need of a holiday, but also for Jewish comedians looking to strike it big. Careers were made on the stages of legendary Catskills resorts like the Concord and Grossinger's, and nearly every Jewish comic of the time performed at one of the area's many hot spots.

Some Borsht Belt comedians like Jerry Lewis came from entertainment families who lived and breathed showbiz. Others crept in as tummlers (basically warm-up guys), or as busboys, bellboys or social directors.

Borscht Belt humor is characterized by stereotypical Jewish traits, such as self-deprecation, insults, complaints, marital bickering, Hypochondria, wordplay and liberal use of Yiddish. The Alter Kocker character type (a senior citizen with a Yiddish accent) was developed here as well.

Some examples of Borscht Belt humor:

I just got back from a pleasure trip. I took my mother-in-law to the airport.

I've been in love with the same woman for 49 years! If my wife ever finds out, she'll kill me!

Someone stole all my credit cards but I won't be reporting it. The thief spends less than my wife did.

The Doctor gave a man six months to live. The man couldn't pay his bill so the doctor gave him another six months.

Why do Jewish divorces cost so much?
They're worth it.

There is a big controversy on the Jewish view of when life begins. In Jewish tradition, the fetus is not considered viable until it graduates from medical school.

A Jewish boy comes home from school and tells his mother he has a part in the play. She asks,

"What part is it?"

The boy says, "I play the part of the Jewish husband."

"The mother scowls and says, "Go back and tell the teacher you want a speaking part."

Q: How many Jewish mothers does it take to change a light bulb?

A: (Sigh)"Don't bother. I'll sit in the dark. I don't want to be a nuisance to anybody."

American Jewish standup, and to some extent the resorts serving as a home to it, died when television came in, with Danny Kaye leading the way into TV and movies. But it almost certainly also died of acceptance and assimilation. The decline of the Catskills resorts was apparent as early as 1965. Entertainment in America was changing as the country ushered in the jet age.

As ethnic barriers in the U.S. began to fall and travel to distant resorts became easier and cheaper, fewer Jewish American families in New York City went to the Catskills. By the early 1960s, between a quarter and a third of Grossinger's annual visitors were non-Jewish. Even the widespread appearance of air-conditioned hotels across America drew customers away from the aging resorts primarily built before this innovation became popular. In the social and cultural upheavals of the 1960s, traditional resort vacations lost their appeal for many younger adults.

It may ultimately be impossible to fully understand the unique alchemy that gave rise to the Jewish Catskills resorts experience. What the Catskills was, it will never be again. It could only have existed when and where it did. Within that relatively small area of bad farmland in New York’s Sullivan County, nestled in the Catskill Mountains, the famed Borscht Belt emerged. And what went on at these dozens upon dozens of Jewish, family-run hotels would impact American vacation and pop culture forever.