Margaret Sample was born on August 19, 1846, in North Carolina to William and Jane Sample. Her father was a farmer who owned $18,500 of real estate and $23,300 of personal property by 1860. She grew up and attended school in Charlotte, North Carolina. She lived next to Samuel J. McElroy, and he eventually began courting her.
The couple got married on January 19, 1866, and they had at least eight children: William, born around 1867; Henry, born around 1869; John, born around 1873; Carrie, born around 1875; Flora, born around 1878; Eugenia, born around 1880; Mattie, born around 1884; and Una, born around 1887. They lived in Long Creek, North Carolina, and her husband worked as a farmer. By 1870, they owned $2,000 of real estate and $500 of personal property. Her husband died on November 5, 1927, and she died of a cerebral hemorrhage in Long Creek on December 28, 1928.