Martha Elizabeth McMahon (maiden name: Fuller) was born on September 14, 1840, in Alabama to William and Emily Fuller. Her father was an innkeeper who owned $3,500 of real estate and $6,000 of personal property by 1860. The family lived in Butler County, Alabama, until around 1858, when they moved to Newton County, Texas.
She married Friend R. McMahon on October 11, 1860, and they had at least seven children: Jesse, born around 1866; Lena, born around 1868; Francis, born around 1869; Martha, born around 1871; Emma, born around 1873; Robert Lee, born around 1875; and Benjamin, born around 1877. They lived in Newton County, and her husband worked as a farmer. By 1870, he owned $2,500 of real estate and $500 of personal property. By 1900, they were living in Justice, Texas. Her husband died on January 10, 1916. She died of apoplexy in Wichita Falls, Texas, on May 17, 1925.