Henry Cronig’s desk is still in the front office where he customarily sat, smoking a cigar, near a wall-sized map of the world where he used to track his travels with pushpins. And Cronig’s Real Estate is still doing business out of the same Main street Vineyard Haven building where Henry founded his company 100 years ago in a partitioned-off corner of the family store.

It didn’t take Mr. Cronig long to leave the grocery business he and his older brothers Sam, Edward and Theodore had founded in 1917 after coming to New England from Lithuania a few years before. Mr. Cronig struck out on his own as a Martha’s Vineyard real estate agent soon after the first Cronig’s Market opened its doors, by brokering the sale of an Oak Bluffs gas station from one of his grocery customers to another.

His $350 commission for the deal was eye-opening, Mr. Cronig wrote in the Gazette in 1964.

“Well! Here I had been working my head off selling black pepper, riceflakes and bologna, and with a little talk, I had earned that amount of money. This, I thought, was real business. No spoiled fruit, no ice bills, no short weights! This was the life!”

Henry Cronig soon began buying and selling properties, on his own and with partners, eventually becoming the largest landowner in the town of Gay Head (now Aquinnah), with many other holdings around the Island.

“Good friends of mine tried to discourage me in this,” he wrote. “But I said, ‘This might not be the right thing for you to do but it’s the right thing for me. I have got the time to wait.’ And it paid off.”

Mr. Cronig ran the real estate company on his own until at age 50 he realized he was in danger of what is now called burnout.

“I got to thinking,” he wrote. “It was no trouble to make money, but how long can I keep up the pace?”

Mr. Cronig solved his dilemma by bringing his nephew Carlyle Cronig, Sam’s second son, into the real estate firm. Carly Cronig, as he was long known, was a Harvard graduate and World War II veteran who had recently returned to the Island. He would run Cronig’s Real Estate until his retirement in 2002, when his son Peter took over the business.

Freed from the daily chores of running the company, Henry Cronig “took off for Africa and I haven’t answered the phone since,” he wrote in 1964. He began selling off his Island landholdings, helped found the Martha’s Vineyard Hebrew Center and donated the property for the Hebrew Cemetery in Vineyard Haven.

“He also sold a lot of real estate to veterans at very low prices,” said Neal Stiller, a nephew of Carly Cronig who has been a broker with the real estate company for the past 35 years.

Succeeding his uncle at the helm of the firm for more than half of its 100-year history, Carly Cronig built a long-lasting reputation as a businessman of integrity in the small, but growing, Martha’s Vineyard real estate industry.

“Peter’s dad was known as the most honest real estate agent on the Island for decades,” Mr. Stiller said. “I was thrilled to train under him.”

Henry Cronig died in 1972. Carly Cronig died in 2009.

Peter Cronig recalled his father as hard working to a fault: “For his time, he did an enormous amount of summer rentals,” he said. “My mother never saw him in the summer. He was always meeting the boat.”

“We all did that for years,” Mr. Stiller said. “I personally stopped doing summer rentals about 20 years ago, after one summer when I did close to 50 rentals and my head hurt all summer from all the problems,” he said, recallng late-night calls about broken washing machines.

Cronig’s Real Estate still handles some seasonal rentals, though brokers stand to earn much more than the $100 or so they used to make. “It’s a higher end market, so the reward is greater,” Mr. Stiller said.

The company also connects tenants with year-round rentals. “I enjoy those, though of course we never have enough,” Mr. Stiller said. “The tenants in those treat the house or apartment like they own it — they’re so happy to have a year-round rental. We’ve had year-round tenants in houses for 20 years.”

But as with other Island realty companies, the bulk of the business is in sales, of both residential and commercial properties. “We do probably the most commercial sales of anybody in Vineyard Haven,” said Peter Cronig, over the sound of construction from the new Asian restaurant next door to his office.

When it comes to residential property, “I pride myself on selling to year-rounders,” Mr. Stiller said. “I like to help the first-time homebuyer.”

That’s a tall order in the Vineyard real estate market, where multimillion-dollar listings abound with few homes priced for entry-level buyers.

“It’s my children’s friends who are buyers here, who grew up playing at my house,” Mr. Stiller said. “They’re in their late twenties and their early thirties and they’re trying to buy, and it’s just tough. If something comes on (the market) in their price range, it’s gone in a day.”

This state of affairs is bound to change, Peter Cronig said, noting the cyclical nature of real estate is something his company has seen many times over its 100-year history. “After the crash [in 2008], house prices dropped,” he said.

“We hope it’s not the same kind of bubble,” he added.