Mary D. Williams was born on December 26, 1837, in Wales. She immigrated to America around 1855 and settled in Pennsylvania. She married William D. Rees on October 8, 1861, and they had no children. Her husband served in the Union army, and he died on August 25, 1862. She applied for a widow’s pension the following month and eventually received one.
She married Henry Rees, and they had at least three children: Thomas, born around 1869; Samuel, born around 1870; and Margaret, born around 1876. They lived in Broad Top, Pennsylvania, and her husband worked as a coal miner. By 1870, they owned $400 of real estate and $150 of personal property. Her husband died on November 30, 1896, and by 1900, she was living in her son Thomas’s household in Broad Top. She died on November 14, 1918.