Among his opponents were Elmer Carter, a Republican member of the state’s new Commission Against Discrimination, and Andronicus Jacobs, a longshoreman who’d fought to secure equal pay and benefits for black dock workers and ran on the American Labor Party ticket.

Born in St. Lucia, Mr. Jack immigrated to the United States as a teenager in 1923. He started out sweeping floors in a box factory while taking night classes before going on to N.Y.U. Along the way, he took an interest in politics, and began canvassing for the Democrats in Harlem.

As a dutiful Catholic and longtime party organizer, Mr. Jack was an apt choice as Tammany’s candidate by 1953. He also had a distinguished record as one of the first black lawmakers from Harlem elected to the State Assembly, starting in 1940. He voted along the Tammany line. But he also emerged as a consistent and cleareyed advocate for bills aimed at dismantling segregation and discrimination in housing, education and policing. In 1945, he helped pass a bill that made New York the first state to bar race and religious discrimination in employment.

Mr. Jack’s daily and long-term work in the borough office — whether turning vacant lots into playgrounds or supporting selective slum clearance instead of wholesale demolition — often focused on issues affecting working-class residents. He ultimately opposed Robert Moses’ ill-fated expressway across Lower Manhattan, which many now agree would have irretrievably altered the city. But he also helped facilitate Mr. Moses’ grand plan for Lincoln Center, insisting on a fairer timeline for relocating residents of the neighborhood.

He also kept a high profile amid national and international personalities: In photos from those years, he can be seen shoulder to shoulder with people like Mr. Moses, John F. Kennedy and Mayor Robert Wagner, and while in office he met with African leaders including the prime minister of Ghana, Kwame Nkrumah, and the Ethiopian emperor Haile Selassie. He became a symbol to the rest of the world that a black man could rise to such a station.