Former U.S. first lady Nancy Davis Reagan died this morning at her home in Los Angeles at the age of 94. The cause of death was congestive heart failure, according to her spokesperson.

Known through the 1980's and 1990's as the face of campaign to end youth substance abuse, and for her catchphrase, "Just Say No," Reagan remained an active champion of many causes -- principally for Alzheimer's research -- to combat the disease that claimed her husband, former President Ronald Reagan.

She will be buried at the Ronald Reagan Presidential Library in Simi Valley, California, next to her husband, who died on June 5, 2004.

When Ronald Reagan was governor of California, Nancy Reagan assisted wounded Vietnam veterans and worked with the elderly and with physically and emotionally disabled children. She later promoted a Foster Grandparent program that brought together seniors and disabled children.

After leaving the White House in 1989, Reagan established the Nancy Reagan Foundation to continue her campaign to educate children about the serious dangers of substance abuse. She later worked to develop the Nancy Reagan Afterschool Program, a drug prevention and life-skills program for youth.

Reagan became her husband's caregiver as he battled Alzheimer's Disease, which led her to become a champion for Alzheimer's studies.

She promoted stem cell research, a topic that put her at odds with Reagan's Republican Party, in which he has, in recent years, gained a cult-like following and heroic status.

After his death, Nancy Reagan worked on projects related to the Ronald Reagan Presidential Library in Simi Valley, California.

Born on July 6, 1921, in New York City, Reagan was raised in Chicago. She went on to Smith College, Northampton, Mass., where she graduated in 1943.

A stage, film and TV actress early in her career, she signed a seven-year contract with MGM in 1949.

It was during that time she met Ronald Reagan and they were married on March 4, 1952. She made 11 films in all, including three after her marriage. Her last film, at Columbia in 1956, was "Hellcats of the Navy," the only film in which she and her husband appeared together, according to the Ronald Reagan Presidential Library biography.