John Mitchel was born in Fordham, New York in 1879. The grandson of John Mitchel, the Irish nationalist leader who emigrated to the United States in 1853.

Mitchel became a lawyer and in 1906 took part in an investigation of corrupt New York City officials. In 1913 he was elected as the youngest mayor in the city's history. He introduced a number of civic reforms including a program of tax relief. However, he was removed from power in 1917 by Charles Murphy and the powerful Tammany Society.

When the United States entered the First World War Mitchel joined the Aviation Corps. John Mitchel died in an aircraft accident in 1918.