He married Sarah Helen Frelinghuysen Davis July 24, 1906, at Washington, D.C. McCawley worked in the Commandant of the Marine Corps office as Chief Clerk from 1881 to 1897.

Captain McCawley was assigned as quartermaster (supply and logistics officer) of the First Marine Battalion on April 19, 1898, at New York Navy Yard in Brooklyn.

The First Marine Battalion (Reinforced) was transferred to the North Atlantic Squadron on April 22 and boarded the transport USS Panther for shipment to Key West, Florida.

During that time he participated in battles with the Spanish Army and Cuban irregulars on June 11, 12, and 13 at and near Camp McCalla during operations to capture Guantanamo Bay, Cuba.

On September 23 McCawley was transferred to Marine Corps Headquarters in Washington, D.C. On March 3, 1899, he was promoted to major and assigned as an assistant quartermaster.

On March 18, 1900, McCawley received a brevet (honorary promotion) to major for distinguished conduct and public services in the presence of the enemy at Guantanamo Bay on June 11, 1898.

On September 27, 1918, McCawley accompanied Major General Commandant George Barnett to France on a tour of inspection before resuming his duties on December 16, 1918, as The Quartermaster of the Marine Corps.