Mackie enlisted in the Marine Corps from
New York on April 24, 1861. His first assignment was with the
Marine Detachment on board the USS
Savannah. He was promoted to corporal on March 1, 1862. On April 1, he began serving on the
ironclad warship USS
Galena. On May 15, a five-ship
Union Navy squadron, including the
Galena, steamed up the
James River to test the defenses of the
Confederate capital,
Richmond, Virginia. After reaching a bend in the river upstream of
Dutch Gap, the squadron encountered submerged obstacles and heavy fire from two battalions of Confederate Marines positioned on the banks of the river and artillery fire from
Fort Darling atop
Drewry's Bluff about eight miles below Richmond. Mackie commanded 12 Marines on the gun deck. The fort's
artillery batteries inflicted severe damage on the
Galena and forced the Union squadron to turn back. During the battle (which would come to be known as the
Battle of Drewry's Bluff), most of
Galena's naval gun crew was killed or wounded. Mackie led a group of Marines who took over operation of the guns for the remainder of the battle. On November 1, he was promoted to orderly sergeant. In June 1863, he was assigned to the . On July 10, 1863, Mackie was awarded the Medal of Honor (Navy version) for his actions aboard the
Galena on May 15, 1862. Mackie was particularly mentioned for his "gallant conduct and services and signal acts of devotion to duty". On October 11, 1863, he received the medal by U.S. Postal Service mail while aboard the
Seminole which was anchored off Sabine Pass, Texas. Mackie was presented the Medal of Honor during a ceremony on the
quarterdeck of the ship. He was
honorably discharged from the Marine Corps on August 23, 1865, in
Boston. Mackie and Sergeant
Pinkerton Vaughn (, 1863) were the first Marines to be awarded the Medal of Honor. Mackie eventually married and settled near
Philadelphia. He died at the age of 74 and is buried in
Arlington Cemetery, in the
Drexel Hill section of
Upper Darby, Pennsylvania. At Drewry's Bluff, now within
Richmond National Battlefield Park, a marker is posted which features Mackie's Medal of Honor action. ==Medal of Honor citation==