Locke was born in Vermont. He married Belle Augusta Fisher (Locke) (1861–1915) on September 2, 1880. William and Belle had two children: Florence Locke (1883–1972) and John Fisher Locke (1887–1925).
In 1910, William, Belle, Florence and John lived at 26 Moss Avenue, along with a servant named Clara Carlson. John attended Harvard University c.1911–1913.
Death and Burial
Locke died in 1915, and is buried in plot 24 in the Fisher family lot along with the Belle, Florence and John. Also buried there are Belle's parents, Charles Anson Fisher (1827–1905) and Mary Patterson Ryer Fisher (1830–1896), Belle's sister Emma Fisher Andrews (1873–1960) and her husband Jesse Swett Andrews (1867–1934).