Reuben G. Clark Jr., 89, a tax lawyer who was a founding partner of the Washington law firm of Wilmer, Cutler & Pickering and who was an authority on urban renewal and human rights issues, died June 6 at the Hospice of the Piedmont in Charlottesville. He had kidney failure, his son Stephen E. Clark said.

Mr. Clark came to Washington in 1952 to work as a lawyer with the Treasury Department. In 1954, he formed a tax law firm with Samuel Jackson Lanahan called Clark & Lanahan. Their firm later merged with Wilmer & Broun, which in 1962 joined another law firm to create Wilmer, Cutler & Pickering (now Wilmer­Hale).

Before his retirement in 1989, Mr. Clark worked on many projects involving urban renewal and was considered an authority on the Department of Housing and Urban Development’s New Communities program of the 1960s. He served on a presidential commission on urban housing during the Lyndon B. Johnson administration and chaired a D.C. citizens advisory committee on urban renewal.

Mr. Clark took a sabbatical in 1975 to work in Kenya for the International Monetary Fund. From 1976 to 1979, he headed Wilmer, Cutler’s London office, where he was involved in international arbitration matters and nuclear power regulations.

He also helped launch the Southern Africa Legal Services Foundation, which provided legal support to challenge the rule of apartheid in South Africa. Mr. Clark served as the foundation’s first president, from 1979 to 1990.

He was also a founder, in 1963, of the Lawyers Committee for Civil Rights Under Law, a group that provides legal services to address racial discrimination.

Reuben Grove Clark Jr. was born Jan. 30, 1923, in Savannah, Ga., and grew up near Albany, N.Y. He was a graduate of the private Woodberry Forest School in Orange, Va., and graduated from Yale in an accelerated wartime program in 1943.

He served as an officer aboard a Navy destroyer during World War II. After graduating from Yale law school in 1948, he spent a year at the University of Cambridge in England on a fellowship to study economics and taxation.

Mr. Clark taught at Howard University law school in the 1950s and 1960s and later was an adjunct professor of law at George Washington University and the University of Virginia.

He was also a longtime member of the Society of the Cincinnati, a heritage organization devoted to the history of the Revolutionary War. When Mr. Clark was president of the society from 1986 to 1989, he was instrumental in restoring its Northwest Washington headquarters, the Anderson House.

In retirement, Mr. Clark settled on a farm near Charlottesville but maintained a home in Washington. He served as chairman of the Charlottesville-Albemarle board of the Piedmont Environmental Council.

Survivors include his wife of 62 years, Mary Ellen Ronald Clark of North Garden; three children, Reuben G. Clark III of Raleigh, N.C., Melissa W. Clark of Washington and Stephen E. Clark of Reston; and four grandchildren.