Thirty years ago, filmmaker and writer Lloyd Handwerker started researching the family business. He wanted to know how Nathan’s Famous, the Coney Island hot dog eatery, become an American icon.

In July 1916, Nathan Handwerker opened what would eventually become the most recognizable hot dog stand on the planet. It started on the corner of Surf Avenue and Schweikert Walk, a five-foot counter with a sand floor known for selling five-cent frankfurters and cups of steaming fries. It grew to encompass a city block.

Family tensions arose as Nathan’s sons Murray and Sol stepped into management roles. The family sold Nathan’s for $22 million in 1984. The brand is now an economic powerhouse that sells 500 million hot dogs a year at locations across the globe. The original location still stands, a symbol of old New York and home of Coney Island’s annual Fourth of July hot dog eating contest.

In time for the company’s centennial comes “Famous Nathan: A Family Saga of Coney Island, The American Dream, and the Search for the Perfect Hot Dog,” written with Gil Reavill (Flatiron Books, 306 pp., $26.99), a companion piece to Lloyd’s 2014 documentary. The book explores Nathan’s impoverished childhood in Poland, his daunting journey to the United States and the hard work that led to his success. The story is set against the backdrop of 20th-century events: the glory days of Coney Island, two world wars, the Great Depression and the sinking of the Titanic, just one week after Nathan crossed the Atlantic.

Lloyd Handwerker spoke to Newsday by phone; an edited version of our conversation follows.

Why did you decide to research Nathan’s Famous?

I was 17 when my grandfather died. I didn’t really know him, what he was like as a boss, as a person. I didn’t know why Nathan’s was what it was. Was it luck? I learned a lot about why. It didn’t just happen. It happened because of my grandparents and their workers. I wanted to share that with people, so they know why this place has the reputation it has. It’s amazing how many people have strong memories about the place.

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Was there anything you were surprised to learn?

What surprised me was his volcanic temper. He’d shout, take a walk and get over it. I can’t even imagine. I never saw his temper. He seemed like the sweetest guy on the planet.

Your grandfather has quite the story, escaping poverty in Poland just before the start of World War I, building an empire off nickel hot dogs. What part of it inspires you most?

He was charitable in the sense of old school charity, never forgetting where he came from. He donated to Catholic and Jewish youth leagues. A priest contacted my grandfather once, saying they needed to paint a church. He gave them money, but he didn’t want anyone to know he was doing it.

Where did that come from?

Clearly, his childhood. His mother had a food stand in Poland, certain business ethics she passed on to him. When he was 14, there was a potato shortage. My grandfather bought potatoes from another town, delivered them by horseback. His mother wasn’t going to sell to the highest bidder. She made sure every customer got a bag. I think it’s Jewish values he learned in temple about giving to other people.

A feud developed between Nathan’s sons, leading first Murray and then your father, Sol, to go out on their own. Eventually Murray came back. Why so much family tension?

Praise was not something my grandfather gave. He wasn’t praised by his father. It must have been difficult being his son, comparing yourself to someone who built this place from scratch. He was competitive, very resistant to change and maybe a bit insecure because of his lack of education. The two brothers had different ideas about how the business should expand. They weren’t super close. My grandfather had conflict with his own brothers. It was something that got passed on.

How did Nathan’s garner the reputation for quality?

In some ways it was like a farm-to-table restaurant, they went to the market every day. Made their own roast beef, pork sandwiches — the only thing that wasn’t made there was the frankfurter. My grandfather always called it a frankfurter. If you look at the old pictures of the place, he always used “frankfurter.” I’m sure dog offended him in some ways.