St. Louis Arsenal: Armory of the West - Hardcoverby Randy McGuire (Author) On the afternoon of May 10, 1861, Army Captain Nathaniel Lyon marched out of the St. Louis Arsenal at the head of 7,000 Union Regulars and Volunteers to capture an encampment of nearly 700 reputed Confederate sympathizers at Camp Jackson on the western outskirts of St. Louis. It probably did not occur to him that he was embarking on a mission that would forever enshrine his name, and that of the Arsenal, in the annals of