John Enoch Mason was born on July 11, 1854, at Edge Hill, Albemarle County, Virginia, to Maria Jefferson (née Randolph) and her husband Charles T. Mason, a Virginia state senator representing Stafford, King George and Prince William counties.

[2] At the time, his uncle Benjamin Franklin Randolph (1808-1870) was also serving in the Virginia senate, representing Albemarle County.

During the American Civil War, he was too young to enlist, but another uncle, George W. Randolph represented the city of Richmond at the Virginia Secession convention and was the Confederate Secretary of war and also served in the Confederate Senate (1863-1865).

[3] After admission to the Virginia bar, Mason worked as a lawyer and served as a commonwealth attorney in King George County for three terms.

After the re-organization of the judicial system under the new constitution, Mason was elected judge of the circuit court of the 15th district.