A native of Manhattan, New York City, from 1934 to 1973, Miller was a trustee of the Carnegie Corporation of New York, a grant-making foundation. The foundation was established by her father in 1911. From 1973 until her death in 1990, she was an honorary lifetime trustee.[3]
On April 22, 1919, four months before her father's death, Margaret married Roswell Miller Jr. (1894–1983)[4] at the Andrew Carnegie Mansion at 2 East 91st Street on the Upper East Side. Officiating at the wedding were Rev. William Pierson Merril, pastor of the Brick Presbyterian Church, where Margaret and Mrs. Carnegie were members, and Rev. Henry Sloane Coffin, pastor of the Madison Avenue Presbyterian Church where Mr. Carnegie was a member.[5] Margaret Carnegie's marriage to Roswell Miller ended in divorce in 1953. During the divorce, she lost her Atlantic Beach summer house.[6] Miller had four children: Louise, Roswell III, Barbara, and Margaret, three grandchildren: Gail Boggs, Barbara Sanders and Pamela Morrison Mitchell. Great-grandchildren: Andrew Boggs, Morgan Boggs, Laura Draper, Courtney Sweeney, Dylan Evans.[7]
The plight of Margaret Carnegie as the only child of a millionaire is the subject of Scottish author and columnist Neil Munro's "Carnegie's Wee Lassie" (1902), one of his Erchie MacPherson sketches.[8]
