Friend Robinson McMahon was born on December 5, 1837, in Texas to Isaac and Frances McMahon. His father was a farmer who owned $3,000 of real estate by 1850. He grew up and attended school in Newton County, Texas. By 1860, he was working as a grocer, and he owned $250 of real estate and $250 of personal property. He married Martha Elizabeth Fuller on September 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.
McMahon enlisted in the Confederate army in February 1862, and he mustered in as a private in Company H of the 13th Texas Cavalry. The regiment took part in the Battle of Milliken’s Bend.
He returned to Newton County after the war, and he earned a living 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. He died on January 10, 1916.