 Griffin was admitted to the bar in May 1858 and in November moved to Grand Rapids, where he begin to practice in the office of prominent Western Michigan lawyer Lucius Patterson.After a fire destroyed the offices in April 1860, along with most of the records of Kent County, Griffin returned to Detroit where he was employed in the law offices of Moore until January 1862, when they formed a partnership named "Moore and Griffin".Griffin was commissioned by Governor Austin Blair, as Supernumerary Second Lieutenant in Company C of the Fourth Michigan Cavalry, and was mustered into service on August 13, 1862.