A farmer and politician before the War, he was elected Sheriff of Marlboro County in 1852, and was elected to the State Legislature in 1860, being re-elected in 1863. He had been long in Militia service rising from Captain, to Colonel, to Brigadier General.
In April 1861 he was appointed Lieutenant Colonel of the 8th South Carolina Infantry, and was at First Manassas. In April 1862 he was elected Colonel of the Regiment.
Colonel Henagen led the men on the Maryland Heights, during action at Harpers Ferry on 13 September 1862
"... Captain A.T. Harllee, commanding one of the color companies, seeing the flag fall, seized it and waving it aloft, called to the men to forward and take the breastworks. He, too, fell desperately wounded, shot through both thighs with a minnie ball. He then called to Colonel Henagan, he being near at hand, to take the colors. Snatching them from under Captain Harllee, Colonel Henagan shouted to the men to follow him, but had not gone far before he fell dangerously wounded. Some of the men lifted up their fallen Colonel and started to the rear; but just at this moment his regiment began to waver and break to the rear. The gallant Colonel seeing this ordered his men to put him down, and commanded in a loud, clear voice, 'About face! Charge and take the works,' which order was obeyed with promptness, and soon the flags of Kershaw's Regiments waved in triumph over the enemy's deserted works."
Lt Colonel Hoole relieved Colonel Henagan and was in command of the Regiment at Sharpsburg on 17 September 1862
He returned to duty and led the Regiment on the Fredericksburg, Chancellorsville, Chickamauga and Gettysburg Campaigns. By May 1864, at the Wilderness, he was in command of the Brigade.
He was captured in action near Winchester, Virginia, in the fall of 1864, and was imprisoned at Johnson's Island, Ohio. He died there in April 1865