Helen K. Copley, 81, retired longtime publisher of the San Diego Union-Tribune, died Aug. 25 of pneumonia in the aftermath of a stroke at her home in La Jolla, Calif.

Mrs. Copley, who began working at the newspaper as a secretary, was publisher of the paper and its predecessors for nearly three decades. An avowed conservative like her husband, James S. Copley, she took over after his death in 1973. She had been expected at the time to remain in the background or sell the paper, but instead she worked to keep it in family hands.

She was also prominent in Southern California charities and was listed last year by Forbes magazine as 279th among the nation's richest Americans, with assets estimated at $960 million.

In 1992, she merged the morning San Diego Union and afternoon Tribune into what is now the third-largest newspaper in California. While she was publisher, the newspapers won two Pulitzer Prizes. Upon her retirement in 2001, she handed over Copley Press Inc. to her son, David C. Copley, but she remained publisher emeritus of the newspaper and chairman emeritus of the company.

Born Margaret Helen Kinney in Cedar Rapids, Iowa, Copley served in the Navy WAVES and married in the 1940s. After that marriage ended, she moved with her mother to San Diego in 1951.

She was hired as one of three secretaries to Copley, the company's chief executive, and married her boss in 1965. Eight years later, he died of brain cancer.

Copley Press owns nine daily newspapers and other publications in California, Illinois and Ohio. It also operates the Union-Tribune's Web site, SignOnSanDiego.com.

Mrs. Copley's donated money helped secure a home for the San Diego Symphony and underwrote the library at the University of San Diego. She was one of eight trustees of the Howard Hughes Medical Institute, a biomedical research and education organization.

In addition to her son, survivors include a sister and a brother. She also has two stepchildren from her husband's first marriage, Michael Copley of San Diego and Janice Obre of New York City.