Henry Diamond as New York State Environmental Conservation commissioner in 1973. (Jim McKnight/AP)

Henry L. Diamond, an environmental lawyer and during the past 50 years a key figure in the awakening national concern and sensitivity to issues of natural conservation and preservation, died Feb. 21 at a hospital in Washington. He was 83.

The cause was complications from Parkinson’s disease, said Nathan A. Darling, a family spokesman. Since 1975, Mr. Diamond had been a principal in the Washington environmental law firm Beveridge & Diamond.

Mr. Diamond’s career flourished in large part because of his friendship and political alliance with Laurance Rockefeller, a grandson of Standard Oil founder John D. Rockefeller and a force in national conservation efforts.

As a young law school graduate, Mr. Diamond served on the congressionally created Outdoor Recreation Resources Review Commission, which was chaired by Laurance Rockefeller. The commission examined the needs to designate or expand new parks, and Mr. Diamond edited the final report, which led to conservation measures that came to pass under the Johnson administration.

Mr. Diamond served in a variety of other capacities and positions that helped elevate environmental issues on the national agenda in the years leading up to the establishment of the Environmental Protection Agency in 1970.

That year, he was appointed by New York Gov. Nelson A. Rockefeller (R) — a brother of Laurance’s — as the state’s first commissioner of environmental conservation.

In that position, he once made a 533-mile bicycle ride across the state to promote a $1.2 billion environmental bond issue for water and air pollution control and land acquisition.

In a private role, Mr. Diamond assisted in the legal work that brought about the Rockefeller land gifts to the National Park Service at the JY Ranch in Wyoming, Haleakala National Park on the Hawaiian island of Maui, areas of the U.S. Virgin Islands, and the Marsh-Billings-Rockefeller National Historic Park in Woodstock, Vt. Laurance Rockefeller died in 2004.

Henry Louis Diamond was born in Chattanooga, Tenn., on May 24, 1932. He graduated in 1954 from Vanderbilt University in Nashville, served in the Army and in 1959 graduated from Georgetown University law school.

In his private Washington law practice, Mr. Diamond served on more than 30 boards and commissions involved in water conservation and environmental quality, including Resources for the Future, the Environmental Law Institute, the Woodstock Foundation, the Jackson Hole Preserve Inc., and Americans for Our Heritage and Recreation.

Survivors include his wife since 1961, the former Elizabeth “Betty” Tatum, and a daughter, Laura Diamond, both of Washington.