She’s a highly unusual chief deputy executive for Suffolk County. Attorney Regina Calcaterra is the first woman to hold the post. She’s an East Ender and thoroughly appreciative of life in eastern Suffolk. And her background growing up in Suffolk is extraordinary. She has lived in foster homes and homeless shelters and worse.

She was chosen by the new county executive, Democrat Steve Bellone, as his top aide because he was impressed by the work she did as co-chair of his transition committee.

Although Ms. Calcaterra, 44, had to give up a higher-paying job as managing partner in a 55-attorney New York City law firm, she did so in appreciation of what “public servants in Suffolk County did for me.”

“The social workers and teachers, the foster parents and crossing guards, the police officers and judges — they helped me so,” she recalled.

“I should have been a statistic,” she said.

Her single mother suffered from drug and alcohol abuse. There were five children, each with a different father. “We lived all over Suffolk County,” she recalled. This sometimes involved sleeping in a car and living “on the streets.”

Sometimes her mother “would leave us for a while.”

“The kids would be raising each other,” she added.

At 14, she petitioned a court for emancipation so she could stay in one high school, Centereach High, and she was graduated there.

“All these people who touched us” helped enable her “not to fall through the cracks” and “understand the only way out of poverty was education.”

Ms. Calcaterra put herself through college, graduating as a political science major from SUNY New Paltz. She worked for the Eastern Paralyzed Veterans of America, advocating for disabled veterans and participating in the national drive for passage of the Americans with Disabilities Rights Act of 1990. She served as legislative director for the New York City comptroller’s office, promoting laws to prevent fraud in government. At age 25, she began attending — at night after work — Seton Hall University School of Law.

The law firm she left to take the chief deputy county executive’s job, Barrack, Rodos & Bacine, is internationally recognized for going after corporate fraud. Among Ms. Calcaterra’s biggest legal victories there was representing the New York State Retirement Fund in a lawsuit against WorldCom, Inc. that resulted in a $6.13-billion recovery.

She has been very active in helping young people who are in situations like the one in which she grew up. She is a board member of You Gotta Believe, a group that works to get older foster children adopted.

Ms. Calcaterra returned to Suffolk from New York City in 2006 and settled in the North Fork hamlet of New Suffolk, buying “a cottage I fell in love with. I love the farmland, the vineyards, the waters, the beaches.” Coming home is like “being on vacation.” She lives with two cocker spaniels, Maggie and Oscar, and a cat, Milo.

Her mother died of cancer in 1999. Only in recent times did she meet her father, after having brought and won the first case of its kind in the U.S. allowing an adult child to learn his or her parentage through DNA testing.

She met Mr. Bellone in 2010 when she was nominated as a Democrat to run for the State Senate. He was Babylon Town Supervisor then and she was “tremendously impressed with what he accomplished in Babylon, his vision, his ethics.” She considers her main role as “implementing Steve’s agenda.”

She’s excited to be in the middle of Suffolk County government. “When you work in public service, you have the opportunity to make significant changes for the better.” And she is thrilled to work for a county that has given her so much.

Last month, when the news broke about Samantha Garvey, a homeless Brentwood High School senior who had become a semi-finalist in the Intel Science Talent Search, Ms. Calcaterra jumped at the chance to work with Mr. Bellone to help find a rent-subsidized home for the Garvey family.