These might sound like the memories of someone raised half a century ago in the Jim Crow South. But William “Mo” Cowan is 41 and graduated from high school in 1987.

Four years later, Cowan came to Boston for law school and never left, becoming one of the city’s leading African-American lawyers. Now, he is about to embark on a new journey: Next month, he becomes the fourth chief of staff to Governor Deval Patrick, a job that will put him at the center of nearly every decision the governor makes.

As he does, Cowan follows a path not unlike the governor’s own rise from the South Side of Chicago to the State House. Like Patrick four years ago, Cowan will face the challenge of overcoming a relative lack of political experience.

He is hardly a stranger to sharp elbows, however, as a career litigator groomed at one of the city’s most politically connected firms.

As chief of staff, Cowan will be the governor’s top inside player, a behind-the-scenes manager, enforcer, adviser, and gatekeeper. He is little known in the State House, having come to Beacon Hill just 14 months ago as the governor’s chief lawyer. Many interest groups and legislative staff members have only traded e-mails with him or met with him sparingly.

Cowan clearly has a close bond with the governor. The two met in the 1990s, after Patrick, who had just left the Clinton administration, spoke at a legal event.

“I essentially cold-called him and said: `Hey, you really don’t know me. I’m a young know-nothing lawyer, but you seem to have a handle on this thing. Would you mind sparing a few minutes whenever you can to give me a bit of advice?”‘ Cowan recalled in an interview. “And he said: `Sure. What are you doing right now?”‘

In nearly two decades in Boston, Cowan became a popular mentor for young black professionals and a talent scout frequently called upon to help diversify the city’s institutions. He helped Governor Mitt Romney, who faced criticism for the lack of diversity in his judicial picks, identify lawyers of color who would make good judges. He recruited black lawyers for law firm Mintz Levin and for Middlesex District Attorney Gerard T. Leone Jr.

In his early 30s, Cowan was part of a group of young black professionals who staged “friendly takeovers” at upscale downtown nightspots such as Whiskey Park. Some saw him as an ambassador to fellow transplants who, like him, were once outsiders in an insular Boston.

“People who were new to Boston and were trying find their way would come to Mo, and he would sit down and make time for them and give them advice and tell them who to call,” said E. Macey Russell, a friend and fellow lawyer. “He really became a center for a lot of attorneys, especially attorneys of color. They really knew they could go to him.”

It was a long way from Yadkinville, N.C., the town of 2,200 about 25 miles west of Winston-Salem, where he grew up on a street full of family.

“I lived on one side of the street; I was related to everyone on that side of the street,” Cowan said. “Everyone on the other side of the street was related to each other. So it was close-knit in that sense.”

When Cowan was 16, his father died, leaving his mother to raise him and his two sisters on little more than a minimum wage. Cowan credits his mother and his teachers—some of whom he still keeps in touch with—with helping him become the first Forbush High School graduate to attend Duke University.

He wanted to become a doctor, and “then I took freshman chemistry at Duke,” he said, laughing. After graduating with a degree in sociology, he headed to Northeastern University School of Law.

“I felt I needed to get beyond North Carolina and see the rest of the world,” he said. Boston “was the biggest city I’d ever been in for any extended period of time.”

Cowan spent a decade at Mintz Levin, rising to partner. Patrick persuaded him to give up his lucrative job two summers ago, after inviting Cowan and his wife, Stacy, who is also a lawyer, to the governor’s sprawling retreat in the Berkshires.

“I worked him hard,” Patrick said in an interview. “And we had a really nice dinner. And I got him.”