Fifteen-year-old Clara Thomas slipped up to the balcony at Twelfth Baptist Church in Roxbury. On Sunday mornings, the adults in the lower pews kept their eyes fixed on the pulpit, while the teenagers sat upstairs, trading handwritten notes and giggling.

It was on this day in 1958, Thomas recalled, when the Rev. Dr. William Hester, a regal man with graying temples, calmly rose to begin his Sunday sermon. Just as he was about to preach, a young man walked in.

“Well, well, well,’’ pronounced Hester. “If it isn’t Martin Luther King Jr.’’

The church erupted. And the teenagers sat up straight.

When King stood in the pulpit that morning, he was back on familiar ground. Seven years had passed since he first arrived in Boston in pursuit of his doctorate. Though he preached at other places, Twelfth Baptist was his church home in the city.

Twelfth Baptist, and Boston itself, occupies a treasured space in the story of Martin Luther King Jr., the eloquent Baptist pastor who rose to national prominence as a civil rights leader and whose assassination, 50 years ago this week, still reverberates in memory.

Before the world knew his name, King — born Michael King Jr. — was a young divinity student from Atlanta, studying at Boston University in the early 1950s, preaching in Lower Roxbury, and charting his own destiny. Here, he shaped his thinking on nonviolence; here, he won some independence from the long shadow of his preacher father and namesake; here, he formed friendships to carry through life; here, he found the woman he would marry, the dignified and beautiful Coretta, who once sang in the Twelfth Baptist choir.

The Globe, through interviews, historical retrospectives, and other materials, has reconstructed a portrait of King’s formative years in Boston, when he was a leader in the making but hadn’t stepped into the civil rights fray.

He wasn’t MLK yet, but there was something about him that everyone sensed.

After the sermon that Sunday morning, Thomas and her childhood friend decided to meet King before he was whisked away.

“Let’s go,’’ said Thomas, who is now Clara Bell, the church’s secretary.

“We can’t,’’ the friend said. “Rev. Hester told us not to move.’’

They raced downstairs anyway, just as a head deacon was escorting King into a waiting area at the back of the sanctuary.

“Dr. King,’’ the deacon said jokingly, “these are some of our disobedient children.’’

King smiled at them and said: “It’s so nice to meet you.’’

Green Chevy

King came to Boston in summer 1951 in a green Chevy. By then, he was a graduate of Morehouse College and Crozer Theological Seminary, and, at just 22, an ordained minister at his father’s Ebenezer Baptist Church in Atlanta.

Martin Luther King Sr., known as Daddy King, had urged his fellow Baptist clergyman and friend Hester to keep an eye on his son, who had been questioning Christian conservatism and seemed increasingly determined to set his own path.

The younger King often clashed with his father over religion and politics. He chafed at the emotionalism in the Baptist pews and his father’s traditional style of preaching.

King was seeking something else, an intellectual style of leadership and worship influenced by minister-scholars such as George D. Kelsey, his theology professor at Morehouse, and Benjamin Mays, the college president, said Clayborne Carson, a King historian at Stanford University.

In Boston, King concluded that while he would join his father’s noble profession in ministry, he would do it his own way.

“He knew what he had to do to get ahead as a minister, but he had to do it on his own terms. He didn’t want his father dictating that to him,’’ Carson said.

At Daddy King’s urging, his son also reached out to some Atlanta contacts at Twelfth Baptist: Barbara Wright, his former baby-sitter; and Mary Powell, a part-time secretary at the church.

Powell was also a New England Conservatory of Music graduate student and friend of another conservatory student named Coretta Scott.

Hester and his wife, Beulah, lived on Highland Street in Roxbury, said the Rev. Michael Haynes, who was a Twelfth Baptist pastor for 40 years. Their home became a hip gathering spot for graduate students, and Hester was grooming young seminarians such as King and Haynes.

As a minister in training, King was honing his oratorical skills. At Crozer, where he was one of six black students in his class, he had faced criticism that his sermons were too intellectual and lacked passion.

“Gradually, he found a middle ground that made him distinctive as a Baptist minister who would preach with emotional and intellectual power,’’ Carson said.

Sunday church ‘date’

Boston had a lot to offer King beyond an academic home. He moved, Haynes said, in a cohort of other black graduate students attending the mostly white campuses, hosting them at his Mass. Ave. apartment for Bible study and high-spirited philosophical discussion.

These students, including many from the Jim Crow South whose families knew one another, were a tight group. They partied and socialized, and King soaked it in. He had a nice apartment and new car, both financed by his father. With Powell, the church secretary, as his guide to the city, he was on a mission to get his doctorate, but also something more. He was looking for a wife.

In the fall of 1951, Jewelle Taylor, then a freshman at Radcliffe College, went out on six dates with King, including three times they went to services at different churches in Roxbury.

Taylor, who was from Connecticut, received a phone call from King, then a stranger to her, a thoughtful man with a slow, baritone, Southern voice. King assured her that their fathers were old friends, both of them Baptist preachers. After several phone conversations, she agreed to go to church with him. (The older pastors, she would later learn, were playing matchmaker.)

On their first Sunday church “date,’’ Taylor said, King preached. She was surprised at how confident and smooth he was in the pulpit, “taking command as soon as he was introduced by the pastor,’’ the Radcliffe grad, now 84 and going by Taylor Gibbs, wrote in her book, “Destiny’s Child: Memoirs of a Preacher’s Daughter.’’

Later, the couple enjoyed a big feast at a church member’s house. After two similar outings, she soon realized, she said, that he was testing her interest in him and her “fortitude as a potential . . . helpmate’’ — in other words, the wife of a minister who would return to the South to lead a big church and fight oppressive laws.

“In a way, going to church was his way to see if I was the kind of person who could fit into his life,’’ said Taylor Gibbs in an interview.

King never popped the question, she said. Over time, the pastor’s daughter said going to church was not her idea of a fun date, and she asked King to instead take her to a movie. He seemed disappointed, she recalled, but he rebounded when she hugged him and kissed him on the cheek.

Elated, King bounded down the steps of Moors Hall in Cambridge, humming and singing.

Haynes, the longtime Twelfth Baptist leader, said he met King for the first time on a Sunday at the Hesters’ house. He had heard from the Rev. Hester that King was coming to Boston, and he wanted to greet him.

Both were divinity students born with the same name — Mike. (Haynes still refers to King that way.) Haynes, then the youth minister, is 90, a year older than King would have been today.

That Sunday, Haynes drove King to Twelfth Baptist on Shawmut Avenue. King preached there at least once every month.

“I’m a Roxbury boy, and he was 50 steps ahead of me,’’ said Haynes, who was pursuing a bachelor’s in divinity school while King was working on his PhD. “I never wanted to be in the pulpit when he was there.’’

Leoner Woodson, another longtime church member, recalled seeing King preach there, a sturdy presence at the pulpit in a trim brown suit. Hester ran a quiet church, none of the shouting and stomping for which Baptist churches are often known. At least by comparison to that sober setting, King had a fire in him.

“Back then, if people said ‘Amen,’ everybody would look around,’’ said Woodson, 78.

King, from the start, made a powerful impression, she said. He challenged them to look to the struggle ahead.

“He was saying,’’ she recalled, “that it was up to us to fight for our own rights.’’

Twelfth Baptist, like many other black churches in the city, followed Boston’s early black migration around the early 1900s from Beacon Hill into Lower Roxbury and the South End. The Shawmut Avenue building was a former Jewish temple with stained-glass windows. It became a hub of black life, with socials and potlucks for families who lived nearby.

The church has no record of King’s visits there, save for one photograph of an annual men’s breakfast taken on April 20, 1952. It shows King seated among scores of men in their Sunday best.

Twelfth Baptist, which will memorialize King on Tuesday, eventually moved into its current site on Warren Street around 1958.

Coretta

After six months in Boston, King was starting to get restless about his personal life. He was eager to marry and wasn’t meeting many young women he liked. So one day in January of 1952, he called up his friend Mary Powell, the New England Conservatory of Music student, and asked for her help.

Powell soon afterward called Coretta Scott, an Alabamian and fellow conservatory student who had dreams of being a concert singer.

“Have you heard of Martin King Junior?’’ Powell said to Coretta, according to Coretta’s memoir, “Coretta: My Life, My Love, My Legacy.’’

At first Scott wasn’t interested. She had visions of living in a parsonage, and her future husband in a boring black suit. But she agreed to at least talk with him.

On the phone with King shortly after, Scott still wasn’t impressed. But she agreed to meet him for lunch.

“I have a green Chevy that usually takes 10 minutes to get from BU to the conservatory,’’ he told her. “But I will do it in seven.’’

He picked her up on a Thursday that January. They ate at Sharaf’s Restaurant on Massachusetts Avenue, where they talked about her interest in music, about issues of war and peace and economic justice. King was impressed with her depth of knowledge, and, she said, he grew on her.

As they drove back to their classes after that first date, King impetuously declared: “You have everything I want in a wife.’’

Soon they were dating and going out to parties, where King showed off dance moves like the jitterbug and the waltz. On one of their dates, he took her to see pianist Arthur Rubinstein at Symphony Hall, she recalled in her memoir.

Back in Atlanta, Daddy King had growing concerns about his son. Hester reported that M.L., the younger King’s nickname, had preached a couple of Sundays and attended the church with an attractive young woman. King had had a girlfriend in Atlanta, and there had been talk of an engagement before he decamped for Boston.

That fall, Daddy King and his wife, Alberta, traveled to Boston to see about their son. When the father was alone with the couple, he let it be known that there were other women, women from Atlanta, who had much to offer M.L.

The younger King did not say much.

“He did not want to challenge his father any more than he had already done,’’ Coretta Scott King said in her memoir.

But M.L. had already made up his mind. The next summer he and Scott were married in Atlanta, with Daddy King presiding.

The pledge

As a young man in Boston, King was compiling the pieces of his life: becoming a scholarly minister, finding love, and seeking fellowship with his peers, in part by joining the Sigma chapter of Alpha Phi Alpha, the country’s oldest black Greek fraternity.

The chapter was based at BU, the hub of activity and a magnet for Southern black men seeking their degrees and planning to return home to teach.

Eight young men from the chapter crossed the line — pledged — in 1952 with King, who was older than most of them.

Chapter president Baron H. Martin, now a 91-year-old retired Massachusetts judge, signed off on King and the other pledges.

He has one vivid memory of King as a young pledge: One day he brought the new members to his house, a broad and beautiful Victorian on Waban Street in Roxbury, and tasked them with painting the fence.

But King resisted. As a minister, he was well respected: He had a car, money, and stature. The chore was beneath him.

“He took a pompous stance,’’ recalled Martin. “He pointed out that he was a minister . . . and he wouldn’t do it. He was trying to exert his authority.’’

In response, Martin exerted his. King got a paddle for punishment.

“I hit him so hard — one smack [on the behind],’’ Martin recalled. “You can’t do that anymore.’’

Goodbye, Boston

King completed his academic requirements at BU in 1953 and began working on his doctoral dissertation. In 1954, he and his new bride moved to Montgomery, Ala., where he became pastor of Dexter Avenue Baptist Church, and, in June 1955, he got his doctorate.

That December in Montgomery, a seamstress and budding activist named Rosa Parks launched an era of resistance by refusing to give up her seat to a white person on a city bus. Her arrest for violating segregation laws ignited a bus boycott that King joined and soon led.

The man who had gone to Boston as a student just a few years before, who had preached at Twelfth Baptist and left a deep impression there, was now plainly on his chosen track, one that would change American history and lead him to jail, to fame, and to martyrdom.

Mostly, his focus was on the Jim Crow South, but in 1965, he returned to Boston to lead his first major march in the North against racial imbalance in the schools and shabby housing conditions in city slums.

He used the moment to call for an end to “racial injustice and segregation in every area of life in Boston and America.’’

Each time King came back to town, Haynes would drive him around.

The mourning

Three years later, on April 4, 1968, King was assassinated.

The nation’s cities exploded, and Boston’s black community, too, responded with sporadic violence.

And deep sadness. Hope seemed to have died with him. On April 6, dignitaries and worshipers filled the second-floor chapel of Twelfth Baptist.

“We were terrified,’’ recalled Charles Dawson, a 90-year-old member of the church who attended the service. “It was so sudden. It was almost the same as if he was killed right here in Boston. Everybody was in tears.’’

The mourners sobbed above the strains of the old organ.

“Lord, we bring onto thee the great cause that Martin Luther King espoused,’’ Haynes prayed at the time.

Then the congregation sang: “Precious Lord, take my hand, lead me on . . .’’

Meghan E. Irons can be reached at meghan.irons@globe.com. Follow her on Twitter @meghanirons.