Michael Dowling never said no to a job.

He’s toiled in steel factories, held down construction and plumbing jobs, and worked long hours on the docks on Manhattan’s West Side.

Dowling’s fierce work ethic pushed him toward success, creating a rags-to-riches immigrant story that culminates with his march up Fifth Avenue as grand marshal of the venerable St. Patrick’s Day parade on March 17.

“My mother always said to never forget where you came from,’’ said Dowling, 67, who was born and raised in Knockaderry, a farming village in County Limerick, Ireland.

Growing up, there was no running water or electricity in his dirt-floored home, he recalled in a recent interview. Most of the families in the village were poor.

But today, as president and chief executive of Northwell Health, Dowling leads the state’s largest private employer, with more than 61,000 employees across Long Island, New York City and Westchester.

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“Poverty is the great motivator. I benefited from growing up in that environment,” he said of his humble roots. “If I had to work 24 hours, I would have done it without asking questions.’’

At 17, in the late 1960s, Dowling came to New York to work the docks and make enough money to support his parents and four siblings, while also saving enough to pay for college back home.

“I studied like crazy, determined to do well,” he said.

He went on to earn a master’s degree in social services at Fordham University in the Bronx, where he later became a professor and then dean.

In 1983, he worked in Gov. Mario Cuomo’s administration as director of Health, Education and Human Services, followed by a stint as commissioner of the Department of Social Services. In 2002, he became CEO of North Shore-LIJ, which would later morph into Northwell Health.

“The U.S. opens your mind and gives you a broader perspective,’’ Dowling said, remembering how he was mesmerized by the opportunities that awaited him in New York City when he first arrived.

Marching in the St. Patrick’s Day parade, he said, “is a great opportunity to appreciate Irish culture as part of the American story and the immigration that has been the success of America.”

“It’s a humbling experience to come on the backs of those who came before you,” he added. “You are on their backs. … It’s a history lesson.’’

Even now, when he sees a newly minted immigrant, he instantly recognizes that look of wonderment on their face.

Dowling said it reminds him of the time he walked into a midtown Automat, looking for a cup of tea.

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“The woman handed me a bag with a string at the end and a cup of hot water. . . . I ripped open the bag and spilled the tea into the water.

“I never saw a tea bag before,’’ he said with a laugh.

CORRECTION: A previous version of this story gave the wrong year Dowling began working in the administration of Gov. Mario Cuomo.