Washington (CNN) -- Dorothy Height, a leading civil rights pioneer of the 1960s, died Tuesday at age 98, Howard University Hospital confirmed.
Height died at 3:41 a.m., said hospital spokesman Ron Harris. No cause of death was given.
Height, who had been chair and president emerita of the National Council of Negro Women, worked in the 1960s alongside civil rights pioneers, including the Rev. Martin Luther King Jr., future U.S. Rep. John Lewis and A. Philip Randolph. She was on the platform when King delivered his "I Have a Dream" speech at the 1963 March on Washington.
President Obama called her a hero and the "godmother" of the movement, noting she "served as the only woman at the highest level of the civil rights movement -- witnessing every march and milestone along the way."
"And even in the final weeks of her life -- a time when anyone else would have enjoyed their well-earned rest, Dr. Height continued her fight to make our nation a more open and inclusive place for people of every race, gender, background and faith."
Friend and former U.S. Labor Secretary Alexis M. Herman said she was "deeply saddened" by Height's death.
"She was a dynamic woman with a resilient spirit, who was a role model for women and men of all faiths, races and perspectives," Herman said. "For her, it wasn't about the many years of her life, but what she did with them."
Height's years of service span from Roosevelt to the Obama administration, the council said in a statement announcing her death and listing the highlights of her career.
Height was awarded the Presidential Medal of Freedom in 1994 by President Clinton and the Congressional Gold Medal in 2004. She was among a handful of key African-American leaders to meet with Obama at the White House recently for a summit on race and the economy.
Her name is synonymous with the National Council of Negro Women, a group she led from 1957 to 1988, when she became the group's chair and president emerita. She was also a key figure in the YWCA beginning in the 1930s.
Height was born in Richmond, Virginia, and grew up in Rankin, Pennsylvania. Her civil rights work began in 1933 when she became a leader of the United Christian Youth Movement of North America. Among the issues she tackled were fighting to stop lynchings and working to desegregate the armed forces.
She experienced discrimination and wrote in her memoir about being turned down for admittance to Barnard College in New York.
"Although I had been accepted, they could not admit me," she wrote in "Open Wide the Freedom Gates."
"It took me a while to realize that their decision was a racial matter: Barnard had a quota of two Negro students per year, and two others had already taken the spots."
At its 1980 commencement ceremonies, Barnard awarded Height its highest honor, the Barnard Medal of Distinction.
Under Height's leadership, the National Council of Negro Women dealt with the "unmet needs of women and their families by combating hunger and establishing decent housing and home ownership programs through the federal government for low-income families."
The organization spearheaded voter registration drives and started "Wednesdays in Mississippi" in which female interracial groups helped at Freedom Schools, institutions meant to empower African-Americans and address inequalities in how the races were educated.
Lewis, the Georgia Democrat and fellow civil rights leader, said Height was fighting for social justice "long before Dr. King and some of us appeared on the scene."
"She was truly a pioneer, and she must be remembered as one of those brave and courageous souls that never gave up, never gave in," Lewis said. "She was a feminist and a major spokesperson for the rights of women long before there was a women's movement."
U.S. Rep. Barbara Lee, the California Democrat who is chairwoman of the Congressional Black Caucus, said Height's efforts "undergirds the work" of the caucus.
She called Height "a bold and brilliant African-American woman who blazed many trails and opened many doors for a countless number of Americans, particularly the empowerment of women and girls, during her lifelong quest for justice."