Elaine Decker Rosensweig, 89, an arts patron, philanthropist and past board member of the Washington National Opera and its predecessors, died Feb. 2 at her home in McLean. She had dementia.

A son, John G. Decker, confirmed the death.

Mrs. Rosensweig settled in the Washington area in the late 1940s. She was a past board member of the Levine School of Music, the Mount Vernon Ladies’ Association preservation group and the Phillips Collection, where she helped start the museum’s artwork lending program.

Elaine Lois Gordon was born in New York to Jewish immigrants from Russia. She was a 1943 graduate of Hofstra University in Hempstead, N.Y., and received a master’s degree in fine arts from George Washington University in 1986.

She was a trustee of the Eastgate Trust, a private partnership that owns industrial real estate in the Washington area. She was a benefactor of the private St. Albans School in Washington.

She was a member of Washington Hebrew Congregation, a Reform synagogue.

Her first husband, Samuel J. Decker, died in 1966 after a 21-year marriage. Her second husband, Stanley H. Rosensweig, died in 1996; they had been married for 28 years. A son from her first marriage, Robert G. Decker, died in 1985.

Survivors include two sons from her first marriage, John G. Decker and David G. Decker, both of McLean; a brother; and a granddaughter.

— Adam Bernstein