McCausland was born on September 13, 1836, in Saint Louis, Missouri. His father was an immigrant from County Tyrone, Ireland; his mother was a native of Botetourt County, Virginia. After they both died in 1843, McCausland and his brothers lived with their grandmother and then their guardian uncle, who moved them to Henderson, Virginia (now). McCausland was graduated first in his class from the in Lexington in 1857. After attending the University of Virginia in Charlottesville for a year, he returned to VMI to teach mathematics. As an assistant to , he helped to command VMI cadets who guarded the scaffolding from which was hanged on the morning of December 2, 1859, in Charles Town, Virginia (now West Virginia).
At the outbreak of the Civil War, McCausland organized the—which became part of the —but turned command of it over to . He then raised a second unit, the 36th Virginia Infantry Regiment, which he led in the early campaigns in the Kanawha Valley in western Virginia. He served under former Virginia governor and United States secretary of war at Fort Donelson, Tennessee, in February 1862 when Floyd infamously fled with his Virginia soldiers rather than surrender to Union general . After Floyd was relieved of his command, McCausland returned to southwestern Virginia, where he would serve, in succession, under William W. Loring, John Echols, Samuel Jones, and Albert G. Jenkins.
After Jenkins was mortally wounded at the Battle of Cloyd’s Mountain on May 9, 1864, McCausland took command of Jenkins’s brigade, performed well, and was promoted to brigadier general on May 24. Soon after, Union brigadier general David Hunter and his new Army of West Virginia targeted Lynchburg, a major Confederate transportation hub, for attack. With Brigadier General John Imboden, McCausland fought a delaying action against Hunter on June 17, giving Lieutenant General Jubal Early time to arrive with reinforcements. Lynchburg was saved, and its citizens presented McCausland with an engraved gold sword, silver spurs, and a new horse.
McCausland then joined with Early in the first phase of the latter’s Shenandoah Valley Campaign, which involved moving north into Maryland, Pennsylvania, and eventually to the outskirts of Washington, D.C. In part to avenge the Union burning of parts of the Shenandoah Valley, Early sent McCausland to Hagerstown, Maryland, where he demanded and received ransom; then, under Early’s orders, McCausland moved farther north to the town of Chambersburg.
Located about twenty-five miles northwest of, Chambersburg—the Franklin County seat with a population of about five thousand—briefly had been a staging point for John Brown in 1859 and had already been occupied twice—in October 1862 by Major General cavalry and in June 1863 by General . McCausland arrived at the head of a detachment of cavalry on July 30, 1864, with orders to secure from the town a ransom of either one hundred thousand dollars in gold or five hundred thousand dollars in United States currency. Absent that, he should burn it, which he did by the early afternoon. The fire destroyed about five hundred and fifty buildings, left three thousand people homeless, and caused $1.6 million in damages.
After the raid on Chambersburg, McCausland operated for the remainder of the war with his brigade in the Shenandoah Valley, supporting Early against Union general Philip H. Sheridan. After the Battle of Waynesboro in March 1865, McCausland joined Confederate general Thomas L. Rosser for the.
McCausland refused to follow Lee in surrender on April 9, however. With the remnants of his command, he escaped the Union encirclement and shortly thereafter demobilized at Lynchburg. The prosecuting attorney of Franklin County, Pennsylvania, meanwhile, had obtained a warrant against McCausland on the charge of arson. McCausland responded by fleeing to Canada, then England, Scotland, and France, and finally Mexico. In 1867, after receiving indications from Grant that he would not be prosecuted, he returned to the United States and settled on a large estate in the Kanawha Valley of West Virginia.
McCausland remained on his profitable farm until he died of natural causes on January 23, 1927. At the time of his death, he and Felix Robertson were the last of the Confederate brigadier generals still alive. McCausland was buried in Smith Cemetery in Henderson, West Virginia.