Evelyn Smith Munro, 92, a longtime activist who fought for sharecroppers' rights in one of the United States' first racially integrated labor unions, died Feb. 16 at her home in Laguna Beach, Calif. No cause of death was reported.

Mrs. Munro provided crucial early support to the Southern Tenant Farmers Union, formed in 1934 to improve working conditions for sharecroppers and tenant farmers in the South.

Although often overlooked in history books, the union set the stage for the civil rights movement three decades later as a model for social action that united blacks and whites behind the cause of economic justice. It embraced nonviolence, gave leadership roles to women and blacks and won wage increases for its workers.

Hired as a secretary, Mrs. Munro called herself the "Girl Friday" of the union, but her involvement ran deeper than that unofficial title suggests. She supervised the union's headquarters in Memphis and became a trusted associate and close friend of H.L. Mitchell, the Arkansas socialist who co-founded the organization and was its driving force for two decades. She often accompanied Mitchell and other union officers on dangerous missions that brought her face to face with a lynch mob and vigilante patrols that served plantation owners.

Later, as the union's education director, Mrs. Munro produced study materials, edited a newspaper and developed a union songbook. She also was a member of the executive board and coached other women to become union activists.

"She was extraordinarily competent," said Van Hawkins, a historian of the South who wrote a book about the union that will be published soon. "Mitchell said she was the most important woman involved in the union, and he didn't know what he would have done without her."

In his autobiographies, Mitchell, who died in 1989, portrayed Mrs. Munro warmly.

"Evelyn rode the backcountry roads with me, contacting union members at night, dodging the Night Riders on the prowl," he wrote in "Roll the Union On," published in 1987.

The union eventually broadened its operations to California and became the National Farm Labor Union, which recruited a young Cesar Chavez in 1948. One of Mrs. Munro's treasured possessions was a photograph of her marching with Chavez years later after he founded the United Farm Workers union.

Mrs. Munro was born March 15, 1914, in New Orleans to a family of modest means. As a girl, she rejected racist attitudes and befriended the black women who cleaned for her family. When she was older, she was attracted to the ideas of Norman Thomas, the Socialist Party leader who ran for president six times between 1928 and 1948.

"He spoke about the things that eventually molded me. I realized that I belonged to the whole universe and not just one group," Mrs. Munro told the Orange County Register in 2003.

She joined the Socialist Party when she was 21. In 1935, after studying briefly at the University of Mississippi, a party colleague recommended her to Mitchell, who was looking for someone to run the office of his fledgling union. Promised a job for a month, she wound up staying five years.

During that time, Mrs. Munro not only anchored the union's daily operations but accompanied Mitchell on missions fraught with risk. She rode with him as they searched for the body of a union worker reportedly killed by plantation bosses. She was present at sharecroppers' meetings when they were raided by sheriff's deputies and "riding bosses" -- armed men whose job was to intimidate union workers -- and once was chased to the Arkansas border by a carload of men wielding guns and axes.

Another time, she gathered evidence against an Arkansas plantation owner who was holding 13 union members as slaves in retribution for their participation in a protest march. Mrs. Munro and a colleague pretended to be on a picnic and took photographs of the stockade where the workers were imprisoned. The plantation owner was later tried and convicted of peonage.

Mrs. Munro left the sharecroppers union in 1940 to work for the International Ladies Garment Workers Union in Knoxville, Tenn., where she organized workers in two factories. She later moved to New York, working at Columbia University as a personnel assistant for the Manhattan Project. During this time, she met David Munro, a linguist, and married him in 1945.

Mrs. Munro moved to California in 1947 and served as West Coast education and publicity director for the garment workers union.

When she was in her 60s, she went back to college and received a bachelor's degree in social ecology from the University of California at Irvine in 1977. She worked for the university's extension program for 11 years as an editor and writer and retired in 1979.

In Laguna Beach, her home for more than 50 years, she was a community activist who fed homeless people at local parks once a week. A skilled photographer -- her brother Bradley Smith was a noted photographer for Life, Time and other magazines -- Mrs. Munro often donated her work to local charities.