Elizabeth Rees Shearer, 92, a former volunteer history interpreter with Arlington House who challenged Interior Department officials and the Army to preserve the integrity of the historic mansion, died Oct. 24 at Powhatan Nursing Home in Falls Church. She had Parkinson's disease.

For 30 years, Mrs. Shearer conducted tours and performed other duties at Arlington House, the Robert E. Lee Memorial, which is administered by the National Park Service.

She raised questions in December 1981 about two unofficial holiday parties held at the publicly owned and operated home by then-Interior Secretary James G. Watt and his wife. About 200 guests attended the two events -- a small breakfast hosted by Leilani Watt and a cocktail party hosted three days later by her husband.

Mrs. Shearer was so incensed at Watt's use of the public house and staff that she sent him a two-page letter on Dec. 19, 1981, a Washington Post story reported. She criticized Watt for putting "to private use a national memorial for which he is the public trustee."

Criticism from Mrs. Shearer and others eventually led to a House subcommittee investigation and the comptroller general holding the Watts personally responsible for at least $4,500 in entertainment expenses for the parties.

In 1995, Mrs. Shearer again challenged the Interior Department to preserve the historic setting of Arlington House, which overlooks Arlington National Cemetery. She opposed an agreement between the Interior Department and the Army to reduce the remaining 24.4 woody acres surrounding the memorial to expand the cemetery.

"If the conversion takes place, the memorial dedicated by act of Congress will be diminished because the setting will be altered adversely," she wrote in the Washington Times. "The memorial should not be reduced and be made less appealing, less natural, less historic by removing even a part of the remaining woodland area it has occupied since before the Civil War."

Born Elizabeth Ann Rees in the Clarendon section of Arlington, she graduated from Western High School in the District and earned a bachelor's degree from George Washington University in 1932. After college, she led a life of volunteerism to her community and her church.

Over 75 years, Mrs. Shearer served at First Baptist Church of Clarendon as a Sunday school teacher and deacon and in other positions. She also helped start church congregations throughout Northern Virginia.

During eight years on the Baptist Foreign Mission Board, she spearheaded changes in the board's policy to bring equity in salary and working conditions for female missionaries, traveling spouses and other staff. She was also president of the Mount Vernon Baptist Association, a partnership of most Baptist churches in Northern Virginia.

After World War II, Mrs. Shearer joined Arlington's Citizens' Committee for School Improvement, which supported reform of public schools in Arlington. "She was a woman who was not afraid to challenge authority," said a son, Ross Shearer Jr. of Vienna.

In the summer of 1956, when public schools in Arlington and elsewhere in Virginia were threatened with closure because of the state's policy of massive resistance to integration, Mrs. Shearer confronted then-Gov. J. Lindsay Almond Jr. at a cousin's wedding reception in Chester, Va. "The confrontation went on for an hour while other wedding guests looked on incredulously," her family recalled.

Within a few weeks, Almond broke with the Virginia establishment and overturned the policies of the General Assembly so that public schools in Arlington and some elsewhere in Virginia opened with integrated classrooms.

Mrs. Shearer also served for a number of years as a volunteer on the Arlington Bar Association's Appeals Board, which heard complaints against members of the bar and mediated the disputes.

As much as she was a woman of firm convictions, she possessed a keen sense of humor. She "could make an elevator ride funny, and her stories and wisecracks broke down barriers between strangers," said her son Reese Shearer of Emory, Va.

Her husband of 59 years, Ross Sterling Shearer, died in 1997.

In addition to her sons, survivors include three grandchildren.

Elizabeth Rees Shearer challenged Interior Secretary James G. Watt.