Mary Hitchcock (maiden name: Collier) was born around 1832 in Missouri to George Washington Collier and Francoise Morrison. Her mother died around 1835. By 1850, her father was working as a merchant, and he owned $250,000 of real estate. Mary married Henry Hitchcock in St. Louis, Missouri, on May 4, 1857, and they had at least two children: Henry, born around 1858; and George, born around 1867.
They lived in St. Louis, and her husband worked as a lawyer. In 1860, they owned $102,000 of real estate and $44,000 of personal property. A decade later, their wealth had grown to $350,000 of real estate and $40,000 of personal property. Her husband died around 1902. Mary remained in St. Louis, and by 1910, she employed at least three white servants. She hired an additional servant sometime in the 1910s. She died of bronchopneumonia in St. Louis on January 1, 1928.