John Mitchell was born in 1711 in Lancaster County, Virginia. He studied in Scotland at the University of Edinburgh, and returned to Virginia to practice medicine. During this time he studied natural history and botany. Mitchell and his wife moved to England after suffering from poor health, and it was here that he established himself as a botanist. Mitchell was elected to the Royal Society in 1748.
In addition to his work on botany, Mitchell published a work titled An Essay upon the Causes of the Different Colours of People in Different Climates, in which he declared that the first race had likely had reddish and brown skin. Mitchell died in 1768.