Her brother, Johannes von Trapp, says that she died on Tuesday in Vermont. He called her a "lovely woman who was one of the few truly good people".
The family won acclaim throughout Europe for their singing and escaped from Nazi-occupied Austria in 1938.
Their story was turned into the film and Broadway musical. Maria von Trapp is the second-eldest girl and was portrayed as Louisa in The Sound Of Music.
They moved to Vermont in 1942 after visiting during a singing tour and holidaying in Stowe. The family opened and still operates a lodge there.
Maria von Trapp was the last surviving member of the seven original Trapp Family Singers made famous in The Sound Of Music.
Their story was turned into a Broadway musical in 1959 and a 1965 film, which won the Oscar for best picture.
She was the third child and second-oldest daughter of Austrian Naval Captain Georg von Trapp and his first wife, Agathe Whitehead von Trapp.
Their seven children were the basis for the singing family in the musical and film.
The Sound Of Music was based loosely on a 1949 book by Capt von Trapp's second wife, also Maria von Trapp, who died in 1987.
It tells the story of an Austrian woman who married a widower with seven children and teaches them music.
In 1938, the family escaped from Nazi-occupied Austria and performed concert tours throughout Europe and then a three-month tour in America.
Maria von Trapp played accordion and taught Austrian dance with sister Rosmarie at the Vermont ski lodge.
She wrote in a biography posted on the Trapp Family's website that she was born in the Austrian Alps after her family fled fighting from the First World War and that she was surrounded by music growing up.
"Father played the violin, accordion and mandolin. Mother played piano and violin," she wrote. "I have fond memories of our grandmother playing the piano for us after meals."
Her biography on the website also said that she worked as a lay missionary in Papua, New Guinea.
Rosmarie von Trapp, Johannes von Trapp and Eleonore Von Trapp Campbell were born to Georg von Trapp and his second wife.
Johannes von Trapp said of Maria: "There wasn't a mean or miserable bone in her body. I think everyone who knew her would agree with that."