William Amory Underhill, 89, a lawyer and lobbyist who was raised in the Florida Everglades and spent the last half-century lobbying Congress for Florida businesses, notably the citrus industry, died of cancer Sept. 7 at his home in De Land, Fla.

Mr. Underhill also had a home in Washington, where he moved in 1946 to work for the Department of Justice. He was a special assistant in the claims division and later an assistant attorney general in the lands division. He was known for his work on antitrust cases.

In private practice after resigning from the Justice Department in 1952, Mr. Underhill began work almost immediately for the fledgling Florida Citrus Mutual, a growers organization. The growers had been setting a uniform, minimum price for their products, and the Justice Department said they could not.

Mr. Underhill negotiated with the department to settle the matter with a cease and desist order, which was a better deal for the growers. They could have faced more damaging consequences, such as criminal procedures that could have destroyed the group in its infancy, said Bobby F. McKown, the retired chief executive officer and executive vice president of Florida Citrus Mutual, which now has 12,000 members.

Called "Moon" by his friends because of his round, chubby face, Mr. Underhill had a reputation as a low-key lobbyist whose most prominent display of his craft was his annual ritual of giving birthday cakes to members of Florida's delegation to Congress. Of course, the dessert had a small greeting frosted with icing on the top, courtesy of Florida citrus growers groups.

Mr Underhill also had other clients, such as the Kerr-McGee Corp., a gas exploration firm, and the Refractories Institute, a trade organization for brick-makers.

Two projects were of personal interest to him in his later years: helping realize Florida House, a three-story town house on Second Street NE that provided a respite for Florida residents in town, and supporting his undergraduate and law school alma mater, Stetson University in Florida.

At the time of his death, he was Florida House's treasurer, a position he had held since the house was founded in 1973.

At Stetson and its law school, Mr. Underhill had been chairman emeritus of its board of overseers since 1994.

Mr. Underhill was born in Basinger, Fla., to a family of cattle ranchers. Between law school graduation in 1936 and his entry into the Navy in 1942, he was a prosecuting attorney in Volusia County, Fla.

He served in the Navy for three years during World War II as a gunnery commander. He was mostly stationed in New York. During the war, he befriended Bill Kerr, brother of Oklahoma governor and later Democratic senator Robert S. Kerr. Robert Kerr was a friend of President Harry S. Truman, who asked Mr. Underhill to take over the leadership of Young Democrats of America, which he did for one year, 1946.

Despite his lifelong party affiliation, Mr. Underhill was known to work well with people on both sides of the aisle. Four of the cakes he so liked to send the Florida delegation were waiting for his pickup from Florida House the day after he died, said Bart Hudson, Florida House's executive director.

Mr. Underhill leaves no immediate survivors.