Philip Gibbon Hammer, 85, an urban planner and former chairman of the National Capital Planning Commission who was active in the civil rights movement, died of cancer Jan. 21 at the Millennium South River nursing home in Edgewater.

Mr. Hammer, who was born in Philadelphia and grew up in Wilmington, N.C., was a southern Progressive and advocate of racial justice at a time when suggestions of equality for African Americans caused hostility in many parts of the South. Throughout his career, his role in civil rights and political activism intersected with his professional interest in the development of cities.

In the early 1950s, as executive director of the Atlanta Metropolitan Planning Commission, he began a three-year study on consolidating city and county services. It led to the city's expansion from 35 square miles to 118 square miles and sparked what became known as Atlanta's renaissance.

In the same period, he directed a survey on the economic and social costs of segregated public education in the South. The study provided the basis of an influential book, "The Negro and the Schools," by Harry Ashmore, published just before the U.S. Supreme Court's school desegregation decision in Brown v. Board of Education.

Mr. Hammer was a director of the Atlanta Chamber of Commerce, an all-white organization at that time, and of the boards of the interracial Urban League and the Southern Regional Council.

In 1954, he founded an urban economic consulting firm, Hammer, Siler, George Associates, and in 1961 he moved it to Washington. Its clients included the District of Columbia; Charlotte; Norfolk; St. Louis; and other cities. Other clients were the State Department, the Department of Housing and Urban Development, the U.N. Development Corp. and the Ford Foundation.

He retired in 1979 but continued as a consultant for several years.

As the president of the American Society of Planning Officials in the 1960s, Mr. Hammer negotiated its merger with the American Institute of Planners to form the American Planning Association.

He was appointed chairman of the National Capital Planning Commission by President Lyndon B. Johnson in 1968 and continued to serve in that position under President Richard M. Nixon.

In the 1960s, Mr. Hammer played a key role in organizing the Potomac Institute, a Washington think tank devoted to civil rights. He was a member of its original board of directors and later served as president. Among other projects, the institute developed strategies to end workplace discrimination in defense industries.

Mr. Hammer attributed his interest in social questions to the influence of Frank Porter Graham, who was president of the University of North Carolina when Mr. Hammer was an undergraduate. After graduating in 1936, he received a Littauer Fellowship to study public administration at Harvard University.

As part of his studies, he spent a year in Washington working for Sen. Robert M. La Follette, the Wisconsin Progressive. In 1939, he went to work for the Farm Security Administration, where he became chief of program analysis. In 1944, he transferred to the U.N. Relief and Rehabilitation Agency as administrative assistant to Herbert Lehman, the director.

In 1946, he moved to Atlanta.

Mr. Hammer was a trustee of what is now the World Wildlife Foundation. A former Washington resident, he lived in Edgewater and enjoyed sailing on the Chesapeake Bay.

Survivors include his wife of 64 years, Jane Ross Hammer of Edgewater; three sons, Philip Jr., of Alexandria, Thomas R., of Winston-Salem, N.C., and Michael L., of Washington; and four grandchildren.