Developed as a place to raise a family, Long Island — like many other suburban areas that grew and thrived in post-World War II America — is graying.

While new communities on the island were built for baby boomers back when they were babies, the latest wave of new development — country club-style living in communities for people 55 and older — hopes to help ease them into their retirement years and beyond.

Age-restricted housing has been around for decades, but until recently “there hadn’t been that focus on creating a lifestyle for aging baby boomers,” said Michael Dubb, founder and chief executive of Beechwood Homes. Many of these suburban homeowners are now empty nesters who no longer need a big house, don’t want to deal with landscaping or snow removal, and want to live with others who are at the same stage in their lives, he said.

Having sold out the 720-unit Meadowbrook Pointe at Westbury earlier this year, Mr. Dubb is now building three more resort-like “active adult lifestyle communities.” The largest, Country Pointe Plainview, will have 750 age-restricted condo flats and townhomes with first-floor master bedrooms.

Prices at the gated community range from $650,000 to $1.3 million. In less than a year, 215 out of 230 units in the first phase sold off floor plans and computer renderings before construction had even started, said Steven Dubb, a principal. The 80-acre property includes an adjacent shopping center, an amenity-laden clubhouse, two heated pools, tennis courts and a walking trail.

Just don’t call it a retirement community. “People are going there to feel young and act young,” Mr. Dubb said.

If you stay in the neighborhood where you raised your children, he said, “young people move in and you are the old people next door.” By contrast, in these new age-restricted developments, “you are not the old people next door — everybody is running around with an iPhone full of pictures of their grandchildren.”

Age is not a protected class under the Fair Housing Act, and most municipalities allow exclusive communities for older adults because of the recognized need for senior housing programs. The federal Housing for Older Persons Act of 1995 set a requirement that at least 80 percent of the units in an age-restricted community have at least one person who is 55 years or older, and requires the community to publish and adhere to certain policies.

With many baby boomers now in their 60s and 70s, the swell in senior housing “is happening everywhere in the region,” as many older adults move from single-family houses into multifamily developments, said Christopher Jones, senior vice president and chief planner for the Regional Plan Association, a Manhattan-based think tank. “It is happening nationwide.”

But more people on Long Island seem to be choosing to age in place than in other parts of the region. Since 2000, the number of people over 65 has increased by 34 percent on Long Island, compared with between 20 and 28 percent elsewhere in the region, Mr. Jones said.

By 2019, according to the National Association of Home Builders, households headed by someone 55 or older will constitute more than 45 percent of all American households. And developers nationwide hope to appeal to those graying boomers as they downsize.

Mitchell H. Pally, chief executive officer of the Long Island Builders Institute, said taxes for buyers in age-restricted communities are lower than they would be for those buying a single-family home.

The niche market “has exploded” for both sales and rentals developments, Mr. Pally said, estimating that 4,000 to 5,000 age-restricted units have been built on Long Island in the last five years.

For the last 30 years, John and Helene Cranmer, both 67, lived in a four-bedroom, two-and-a-half-bath ranch with a pool on about half an acre in Smithtown. Wanting to make a “life change,” they put a deposit on a $550,000 three-bedroom townhouse with a basement and a two-car garage at Country Pointe Meadows at Yaphank, a 55-and-older community being built by Beechwood Homes. The condo community will have 20 flats and townhouses priced from $469,000 to $574,000.

“We will be cutting our taxes by more than half,” said Mr. Cranmer, who worked in New York City’s Department of Finance. “It offers us comparable living space at a much more affordable cost of living.” They expect to move next September.

In the meantime, they are slowly weeding through “30 years of stuff” and planning a garage sale, said Mrs. Cranmer, a former systems programmer. Looking forward to card games, mah-jongg and pizza night with new neighbors, they are feeling more secure about the future. “If something happens to one of us, the other won’t have to rush to make an extreme lifestyle change,” Mrs. Cranmer said.

With life expectancy rising, assisted living facilities catering to octogenarians and beyond are also popping up. While 55-and-older communities offer independent living for active adults of a certain age, assisted living is for those who don’t need nursing care, but who can no longer manage completely on their own and need help with things like meal preparation, getting dressed, taking medications and social activities.