Lieutenant Archibald Knox Gilchrist was the son of Scotsman Major AJS Gilchrist. At the age of 14 he joined the Department of Education and was appointed as a pupil teacher in Sydney. He then taught near Glen Innes before coming to Ross Hill Public School at Inverell where he was headmaster from 1904 until 1931.
His early military career is unknown although he is believed to have been involved with cadets at school. In 1913 he passed the Cadet Officers' Examinations and was appointed provisional Lieutenant. During World War 1 he played a leading role in local recruiting and the basic training of war volunteers before their departure from Inverell.
In 1916 Lieutenant Gilchrist was Officer in Charge of the First Kurrajong Contingent travelling by train from Inverell to the Narrabri camp, stopping at Warialda and Moree for marches and rallies to gather additional recruits. After the Kurrajongs arrival at Narrabri, Lieutenant Gilchrist returned to Inverell.
His son, Alexander, and a brother served during World War 1; the latter was killed in action at Gallipoli. Lieutenant Gilchrist died at Inverell in 1931.