Early life and marriage
Henry Knox's parents, William and Mary (née Campbell), were of
 His father was a ship builder who, due to financial reverses, left the family for
St Eustatius in the West Indies where he died in 1762 of unknown causes.
Henry was admitted to the
Boston Latin School, where he studied
Latin, arithmetic, and European history.
 Since he was the oldest son still at home when his father died, he left school at the age of 12 and became a clerk in a bookstore to support his mother. The shop's owner, Nicholas Bowes, became a surrogate father figure for the boy, allowing him to browse the shelves of the store and take home any volume that he wanted to read.
 The inquisitive future war hero, when he was not running errands, taught himself French, learned some philosophy and advanced mathematics, and devoured tales of ancient warriors and famous battles.
 He immersed himself in literature from a tender age. However, Knox was also involved in Boston's street gangs, becoming one of the toughest fighters in his neighborhood.
 Impressed by a military demonstration, at 18 he joined a local artillery company called The Train.
1771 advertisement for Knox's shop
On March 5, 1770 Knox was a witness to the
Boston massacre. According to his affidavit, he attempted to defuse the situation, trying to convince the British soldiers to return to their quarters.
 He also testified at the trials of the soldiers, in which all but two were acquitted.
 In 1771 he opened his own bookshop, the London Book Store, in Boston "opposite
William's Court in
 The store was, in the words of a contemporary, a "great resort for the British officers and Tory ladies, who were the ton at that period."
 Boasting an impressive selection of excellent English products and managed by a friendly proprietor, it quickly became a popular destination for the aristocrats of Boston. As a bookseller, Knox built strong business ties with British suppliers (like Thomas Longman) and developed relationships with his customers, but he retained his childhood aspirations.
 Largely self-educated, he stocked books on military science, and also questioned soldiers who frequented his shop in military matters. The genial giant initially enjoyed reasonable pecuniary success, but his profits slumped after the Boston Port Bill and subsequent citywide boycott of British goods.
 In 1772 he cofounded the Boston Grenadier Corps as an offshoot of The Train, and served as its second in command. Shortly before his 23rd birthday Knox accidentally discharged a shotgun, shooting two fingers off his left hand. He managed to bind the wound up and reach a doctor, who sewed the wound up.
Knox supported the
Sons of Liberty, an organization of agitators against what they considered repressive British colonial policies. It is unknown if he participated in the 1773
Boston Tea Party, but he did serve on guard duty before the incident to make sure no tea was unloaded from the Dartmouth, one of the ships involved.
 The next year he refused a consignment of tea sent to him by
James Rivington, a Loyalist in New York.
Henry married Lucy Flucker (1756–1824), the daughter of Boston Loyalists, on June 16, 1774, despite opposition from her father that was due to their differing political views.
 Lucy's brother served in the British Army, and her family attempted to lure Knox to service there.
 Despite long separations due to his military service, the couple were devoted to one another for the rest of his life, and carried on an extensive correspondence. After the couple fled Boston in 1775, she remained essentially homeless until the British evacuated the city in March 1776. Even afterward, she often traveled to visit Knox in the field. Her parents left, never to return, with the British during their
withdrawal from Boston after the
fortified Dorchester Heights, a success that hinged upon Knox's Ticonderoga expedition.