At Atlanta’s King Center flags were lowered to half-staff today out of respect for King, who was by the side of her husband, Rev. Dr. Martin Luther King Jr., throughout his leadership of the Civil Rights movement. She continued his struggle after his assassination in Memphis, TN on April 4, 1968, flying to Memphis just days after his death to lead a march in support of her slain husband.

“I’m more determined than ever that my husband’s dream will become reality,” King said soon after his slaying.

King had been in poor health since suffering a serious stroke and heart attack in 2005.

Former Atlanta Mayor and civil rights activist Andrew Young told NBC’s “Today” show: “I understand that she was asleep last night and her daughter [Bernice King] went in to wake her up and she was not able to and so she quietly slipped away. Her spirit will remain with us just as her husband’s has.”

King’s death was a “monumental loss to the nation and the world at large,” the Rev. Al Sharpton said in a written statement. “She was truly the first lady of the human rights movement. The only thing worse than losing her is if we never had her.”

King wrote a book, My Life With Martin Luther King Jr, and founded the multi-million dollar Martin Luther King Jr. Center for Nonviolent Social Change in 1969. In 1982, the King Center in Atlanta was completed; and the $8.5 million Freedom Hall, adjacent to the Center, was dedicated later that year. The slain civil rights leader’s tomb surrounded by a reflecting pool is the center of the campus.

Coretta Scott King was also responsible for lobbying for her husband’s birthday to be observed as a national holiday and in 1983 President Ronald Reagan signed the bill into law. The first federal holiday was celebrated in 1986.