When Mary Elizabeth Thompson was born in August 1868, in Texas, United States, her father, Warfield W Thompson, was 42 and her mother, Mary J Campbell, was 35. She married Robert Allen Sandefer Sr in 1888, in Texas, United States. They were the parents of at least 2 sons and 2 daughters. She lived in Shawnee, Pottawatomie, Oklahoma Territory, United States in 1900 and Comanche, Oklahoma, United States in 1910. She died on 22 July 1928, in Oklahoma, United States, at the age of 59, and was buried in Tecumseh, Pottawatomie, Oklahoma, United States.