Sandy Allen grew to be 7 ft 7 in tall. She died at a nursing home in her home state of Indianapolis, according to family friend Rita Rose.
The cause of Ms Allen's death is not known. In recent months she had been treated in hospital for a recurring blood infection, along with diabetes, breathing troubles and kidney failure.
Ms Allen weighed 6.5lb when she was born. By the time she was 10 years old, she had grown to over 6ft tall, and by the age of 16 she was 7ft 1in.
In 1974 she wrote to Guinness World Records saying she would like to get to know someone her own height.
"It is, needless to say, my social life is practically nil and perhaps the publicity from your book might brighten my life," she wrote.
In the 1980s she appeared for several years at the Guinness Museum of World Records in Niagara Falls, Canada.
At the time she said: "There were days when I felt like I was doing a freak show. When that feeling came too often, I knew I had to come back home."
Since returning to Indianapolis, Ms Allen had used her height to inspire school children to accept those who are different.
"She loved talking to kids because they would ask more honest questions. Adults would kind of stand back and stare and not know how to approach her," said Ms Rose.
