Timuel Black, who mobilized the political power of the predominantly Black South Side of Chicago, taught others — including a young Barack Obama — how to do the same, and in his final decades compiled oral histories giving voice to his community’s Black working class, died on Wednesday at his home on the South Side. He was 102.

His wife, Zenobia Johnson-Black, said the cause was prostate cancer.

In 1955, soon after he had begun his career as a high school and college teacher, Professor Black saw the Rev. Dr. Martin Luther King Jr. delivering a sermon on television. He was so moved that he immediately flew to Alabama, his birthplace, to meet Dr. King, who was more than a decade his junior. In the coming years, he helped build support networks for Dr. King while commuting between Chicago and Alabama.

In the South, Professor Black also met the labor leader A. Philip Randolph. After Mr. Randolph established the Negro American Labor Council, an advocacy organization, he enlisted Professor Black in 1960 to run its Chicago division. In 1963, Mr. Randolph and Dr. King put Professor Black in charge of organizing residents of Chicago to attend the March on Washington for Jobs and Freedom.

“Dr. King sensed that he needed us elders and the many who, like me, had our heritage in the South, our families having fled the South, and who had experienced the segregated army,” Professor Black wrote in his memoir, “Sacred Ground: The Chicago Streets of Timuel Black,” published in 2019. “And I needed the leadership.”

In 1975, after decades working at high schools, mostly in Chicago, he became a professor of sociology, anthropology and Black history at Loop College, which was later renamed Harold Washington College.

That name change was one of many local developments that might never have occurred without Professor Black’s background maneuvering.

In 1982, Harold Washington, a friend of Professor Black’s from his youth, represented their neighborhood in the House of Representatives. Professor Black and others suggested that he run for mayor. In his memoir, Professor Black recalled that Mr. Washington laughed in response.

“Sure,” Mr. Washington said. “If you get 50,000 new Black voters, and raise a hundred thousand dollars, then I’ll consider it.”

Professor Black started a fund-raising drive and helped organize a voter registration campaign. Ultimately, he and his group told Mr. Washington that they had come up with 263,000 new voters and more than $1 million.

In 1983, Mr. Washington became Chicago’s first Black mayor. Four years later he was re-elected. Loop College was renamed in his honor after he died, while still in office, in 1987.

Professor Black’s last great encounter with history came in his mentorship, starting in the 1990s, of a young Barack Obama.

“He talked to me for hours,” Professor Black recalled in his memoir about one meeting at an Italian restaurant on the South Side, “asking one question after another about how to build a political base on the South Side.”

Even though Mr. Obama “could not code switch to Black English,” Professor Black said, he introduced him to other figures in Chicago politics who, he wrote, “helped him a lot.”

In Mr. Obama’s election as president in 2008, Professor Black saw the strength of his neighborhood and its Black community. “We had a Black president, someone who, although not originally from the South Side, could only have reached those heights via the South Side, through my Sacred Ground,” he wrote, using the same label for the South Side that he included in the title of his memoir.

In a statement published after Professor Black’s death, Mr. Obama wrote, “Tim was a testament to the power of place, and how the work we do to improve one community can end up reverberating through other neighborhoods and other cities, eventually changing the world.”

Timuel Dixon Black Jr. was born on Dec. 7, 1918, in Birmingham, Ala. When he was an infant, his parents moved to Chicago, hoping to find better work opportunities and to escape the terror of Southern racial oppression.

All of Professor Black’s grandparents, including the grandmother who helped raise him, had been enslaved. His father, known as Dixie, worked as a sharecropper in the South and at steel mills and stockyards in Chicago until the Great Depression, when he did odd jobs for neighbors. Professor Black’s mother, Mattie (McConner) Black, was a homemaker.

Professor Black was drafted into the Army in 1943 and fought on D-Day and in the Battle of the Bulge. Before his honorable discharge, he also visited the Buchenwald concentration camp near Weimar, Germany.

“This is what happened to my ancestors,” Professor Black recalled thinking at the time. “I made an emotional decision that when I returned from the Army, that most of the rest of my life would be spent trying to make where I live, and the bigger world, a place where all people could have peace and justice.”

After he returned home, Professor Black graduated with a bachelor’s degree in sociology from Roosevelt University in Chicago. He went on to study sociology and history at the University of Chicago and received a master’s degree there in 1954.

Professor Black’s first two marriages ended in divorce. In addition to his wife, he is survived by his daughter, Ermetra Black Thomas. His son, Timuel Kerrigan Black, died of AIDS in 1993, and his stepson, Anthony Said Johnson, was fatally shot in a robbery in 2002.

During his final decades, Professor Black was largely engaged in producing two volumes of “Bridges of Memory,” an oral history on the migration of Black people to Chicago, and his memoir, which was itself a kind of oral history, assembled with the help of the Chicago community activist Susan Klonsky. These accounts might not have been verified through archival research, but Professor Black argued that his memories, and those of his fellow Black Chicagoans, had a value of their own.

“This process of personal evaluation may serve to help the present and future generations understand the distinctive qualities of the individual lives as well as the collective life of Black folk in Chicago,” he wrote in his memoir. “They might get this or that fact wrong, but this is how they remembered it.”