John Henry (c. 1776 – 1853) was a spy and adventurer of mysterious origins. He sold documents called the Henry Papers to the United States suggesting treason by Federalists on the eve of the War of 1812 with Great Britain. The Henry Papers helped build outrage against Britain which led to the United States declaring war in June 1812.
It is reputed that Henry was born to a well to do family in Dublin, Ireland, probably in the 1770s. (One source states his age in 1812 was 36 indicating he was born about 1776.)
As a younger son, Henry was not entitled to an inheritance and, about 1790, left for the United States to join an elderly uncle named Daniel McCormick, Esq. in New York. (Some sources say his name was McGillivary, others Keane.)
Henry was described as being 5 feet 9 inches tall, blonde and "very handsome".
Henry came to Philadelphia about 1793 and edited a newspaper, Brown's Philadelphia Gazette.
When Henry's financial prospects soured, Henry obtained, through the influence of the British minister to the United States, a commission as a captain in the United States Army, on June 1, 1798. This was during the Quasi-War with France, when the Army was undergoing a great expansion. Henry commanded an artillery company, under Brigadier General Ebenezer Stevens of the New York Militia, while he served as commanding officer of Fort Wood on Bedloe's Island (now Liberty Island) in New York Harbor. He later served at Fort Jay on Governor's Island.
In the Spring of 1799, Henry and his company were ordered to deploy to Northampton County, Pennsylvania to aid in suppressing Fries's Rebellion against Federal taxation.
Henry was the first commander of Fort Adams in Newport, Rhode Island, when the fort was first garrisoned on July 4, 1799. Near the end of 1800 he was transferred to Fort Sumner in Portland, Maine. He served at Portland until he resigned from the Army at the end of 1801.