Smith died of respiratory arrest in the Raleigh Community Hospital shortly after she was brought to the emergency room about 1:25 p.m. Houston time Tuesday, hospital spokesman Michael Leisey said.
President Reagan, upon learning of Smith's death, said: "All America loved her, and she loved America.
"She thrilled us all with her stirring rendition of "God Bless America" and sang with a passion which left few eyes dry," Reagan said Tuesday. "For many years, Kate Smith touched our hearts and souls and made us all swell with the special pride of being Americans.
"America was indeed God-blessed to have Kate Smith as one of her daughters," Reagan said.
Comedian Bob Hope called Smith "a symbol of what's good, as a person and as an entertainer. She was one of the great gals in entertainment."
Smith suffered brain damage during a diabetic coma in 1976 that made it difficult for her to walk or talk during her later years. Diabetes forced the amputation of her right leg above the knee in January, and she underwent a mastectomy May 9.
Smith's ringing voice and bubbly personality charmed and cheered Americans in the dark days before and during World War II.
Within a year after introducing "God Bless America," Smith became such a patriotic symbol that President Franklin D. Roosevelt introduced her to Britain's King George VI in 1939 by saying: "This is Kate Smith - this is America."
Smith, one of the most popular entertainers on Broadway and radio during the 1930s and 1940s, had no formal music training. She called her voice a "God-given gift."
The best known of her 19 million-selling records was "When the Moon Comes Over the Mountain," an ode to the Shenandoah Mountain country of Virginia, where she was born Kathryn Elizabeth Smith, in the town of Greenville on May 1, 1907.
Her songs made the Hit Parade more than 700 times, among them "The Music Goes Round and Round," The Last Time I Saw Paris and White Cliffs of Dover.
Her family tried to discourage her show business ambitions and wanted her to become a nurse, but she gave up nurse training after several months and at 17 went off to seek her fortune.
She grew up in Washington, singing on variety shows and in church socials before heading to Broadway. She got her break in 1926, playing a 5-foot-10, 235-pound character named Tiny Little.
The show, "Honeymoon Lane," was a hit, but critics' barbs about her weight nearly drove her out of the business until agent Ted Collins became her mentor.
The saddest moment in Smith's life was the death of Collins, whom she met while appearing on Broadway in a musical, "Flying High."
Collins became her manager and arranged her radio appearances, first in variety shows and then on the daily "Kate Smith Hour" and a weekly hourlong program.
When Collins had a massive heart attack and lingered near death, Smith swore she would not sing again until he recovered. She kept her word and Collins made what doctors called a miraculous recovery.
In 1938, she discovered "God Bless America," which Irvin Berlin wrote 19 years before but never published because he thought it too syrupy. Smith got sole performing rights to it and debuted "God Bless America" on Armistice Day 1938.
Americans took the song to heart immediately.
Within a few years, Smith was barnstorming the country, singing "God Bless America" at rallies and selling bonds. Called "radio's very own Statue of Liberty," she traveled 90,000 miles during World War II and hosted several bond-selling marathons. One 24-hour blitz raised $110 million worth of pledges to buy bonds.
Her niece, Susan Andron of Raleigh, said Smith "never received one penny" from "God Bless America." "Every penny . . . went to the Boy Scouts of America," Andron said.
Andron said Smith died "with no tears, no apparent pain."
The fame was more than enough to carry Smith into the 1950s. She wrote her autobiography, "Living in a Great Big Way," and hosted a television show from 1951 to 1954.
Smith was in demand again for the 1976 Bicentennial celebrations. Just before Independence Day she went into a diabetic coma that lasted four months. She suffered brain damage and glaucoma, was confined to a wheelchair and watched her weight dwindle to about 140 pounds.
Smith moved to Raleigh to be closer to relatives and began a slow recovery, rarely drawing attention. By September 1982 she was well enough to appear on the nationally televised Emmy Awards.
Two month later, President Reagan - who co-starred with her in one of her two movies, "This Is The Army" in 1943 - presented her with the Medal of Freedom, the United States' top civilian honor.