But much of his impact was felt closer to home. For 37 years he was a towering community figure as the pastor at Canaan Baptist Church of Christ in Harlem, and from 1965 to 1975 he was a special assistant on urban affairs to Gov. Nelson A. Rockefeller of New York. In both posts he was a strong advocate of affordable housing and better schools in the low-income neighborhoods of Upper Manhattan.

Dr. Walker’s work as a civil rights advocate began in 1953, soon after he finished his graduate studies at the historically black Virginia Union University in Richmond. He had met Dr. King while both were students.

The two had been presidents of their classes — Dr. King at Crozer Theological Seminary in Pennsylvania — and they had their first encounter during an inter-seminary meeting.

Dr. Walker joined the fledgling Southern Christian Leadership Conference in 1961 and served until 1964 as its executive director and, unofficially, as Dr. King’s right-hand man. At the S.C.L.C., he devised a structured fund-raising strategy and organized numerous protests, including a series of anti-segregation boycotts and demonstrations in Birmingham, Ala., that came to be known as Project C.

The C stood for “confrontation,” and the project is regarded as the blueprint for the civil rights movement’s success in the South.