Mary C. Dallam (maiden name: Maulsby) was born on March 7, 1827, in Bel Air, Maryland, to Israel David Maulsby and Jane Hall. Her father was a state legislator who owned at least 3 slaves, and he died around 1839. In 1850, Mary was living in Philadelphia, Pennsylvania. She married William H. Gallam in Bel Air on January 22, 1852, and they had at least four children: Jane, born around 1852; Sara, born around 1854; Mary, born around 1858; and Richard, born around 1865. Her husband died on February 22, 1883. As her health declined in the 1890s, she moved in with her daughter Mary and her son-in-law William B. Nelson. She died in Bel Air on June 15, 1905.