LOS ANGELES: Former US first lady Nancy Reagan died Sunday at age 94, a spokeswoman for the Reagan Presidential Library and Foundation in Simi Valley, California said.

Congestive heart failure was the cause of death, spokeswoman Joanne Drake said.

She will be buried next to her husband at the Ronald Reagan Presidential Library in Simi Valley, California, Drake added.

Her marriage to Ronald Reagan lasted 52 years until his death in 2004.

A former actress, she was Reagan's closest adviser and fierce protector on his journey from actor to governor of California to president of the United States.

She rushed to his side after he was shot in 1981 by a would-be assassin, and later endured his nearly decade-long battle with Alzheimer's disease.

Her best-known project as first lady was the “Just Say No” campaign to help kids and teens stay off drugs.

When she swept into the White House in 1981, the former Hollywood actress partial to designer gowns and pricey china was widely dismissed as a pre-feminist throwback, concerned only with fashion, decorating and entertaining.

By the time she moved out eight years later, Mrs. Reagan was fending off accusations that she was a behind-the-scenes “dragon lady” wielding unchecked power over the Reagan administration _ and doing it based on astrology to boot.

All along she maintained that her only mission was to back her “Ronnie” and strengthen his presidency. Mrs. Reagan carried that charge through the rest of her days.

She served as a full-time caretaker as Alzheimer's melted away her husband's memory. After his death in June 2004 she dedicated herself to tending his legacy, especially at his presidential library in California, where he had served as governor.

She also championed Alzheimer's patients, raising millions of dollars for research and breaking with fellow conservative Republicans to advocate for stem cell studies.

Her dignity and perseverance in these post-White House roles helped smooth over the public's fickle perceptions of the former first lady.

She met Ronald Reagan in 1950, when he was president of the Screen Actors Guild and she was seeking help with a problem: Her name had been wrongly included on a published list of suspected communist sympathizers.

They discussed it over dinner, and she later wrote that she realized on that first blind date “he was everything that I wanted. “ They wed two years later, on March 4, 1952. Daughter Patti was born in October of that year and son Ron followed in 1958.

Reagan already had a daughter, Maureen, and an adopted son, Michael, from his marriage to actress Jane Wyman. (Later, public spats and breaches with her grown children would become a frequent source of embarrassment for Mrs. Reagan.)

She was thrust into the political life when her husband ran for California governor in 1966 and won. She found it a surprisingly rough business. “The movies were custard compared to politics,” Mrs. Reagan said.