Haggerty was born on December 21, 1834, in Glasgow, Scotland, the son of Irish parents.
[1] Haggerty enrolled in the 111th New York Volunteer Infantry Regiment in February 1863 and was mustered in as a first lieutenant and adjutant.
[2] In 1869, President Grant appointed him U.S. Consul at Glasgow, but when he arrived the British refused him due to his connections with Irish nationalist movements.
He was shortly afterwards appointed Deputy Naval Officer of the Port of New York.
He was a member of the Grand Army of the Republic and the Irish National League.