Major-General Franklin Gardner was born in New York in 1823. His family moved West and he was appointed to the United States military academy from Iowa in 1839. After his graduation in 1843 and promotion to brevet second-lieutenant of the Seventh infantry he served in the garrison at Pensacola harbor, in scouting on the frontier, in the military occupation of Texas, and in the war with Mexico. He participated in the defense of Fort Brown, and the battle of Monterey, where he was brevetted first-lieutenant for gallant and meritorious conduct.

With the secession of Virginia in April 1861, Pemberton made his way to Washington, D.C. At the urging of his wife but against the remonstrances of his mother and brothers, he refused General Scott's offer of a colonel's commission, resigned, and cast his lot with Virginia. His rank changed quickly over the weeks that followed. On 28 April he became a lieutenant colonel in the Virginia state army. Ten days later he advanced to colonel in that service.