He studied at South Carolina College, and became a lawyer and a cotton planter. In 1847, he was elected to the house of delegates, then became governor of Virginia in 1848. Appointed Secretary of War under Pres. James Buchanan in 1857, he resigned in December of 1860 in reaction to the President's policy at Charleston Harbor. Floyd was later accused of having helped the Confederacy by obtaining arms and material and transferring them to Southern arsenals prior to the War.
After returning to western Virginia to recruit mountaineers, he was appointed a Brigadier General on May 23, 1861. In December of 1861, his brigade was sent to join Gen. A.S. Johnston's army in Tennessee. Floyd's brigade took part in the defense of Fort Donelson in February of 1862. In the face of a surrender to Union troops, he was able to take a steamboat and save most of his brigade, allowing Brigadier Gen. Buckner to surrender the main army. Retreating to Nashville, he left after trying to save supplies there.
On March 11, 1862, he was relieved of his command in Nashville for desertion. Despite his dishonor, he took an active part in the war effort in southwestern Virginia, and was commissioned a major general in the state militia on May 17th.
He raised a band of "partisans," which attacked Union troops and antagonized Confederates by interfering with their recruitment of Regulars. Floyd's health deteriorated by prolonged exposure, and he died near Abingdon, Virginia, on August 26, 1863.