At the onset of the Civil War, Missouri held particular importance as the westernmost border state, a gateway to the western territories, and a state bordered by the Mississippi River. After Union forces suffered a major defeat at Wilson’s Creek south of Springfield, Missouri, on Aug. 10, 1861, the Missouri State Guard under Maj. Gen. Sterling Price moved north to advance upon Lexington. Price, a longtime Missouri public servant who had been speaker of the Missouri House, a United States Representative, Governor, and a Brevet Brigadier General in the Mexican War, now commanded the State Guard. Col. James A. Mulligan, a thirty-two-year-old Chicago politician, commanded the Twenty-third Illinois Infantry, known as the Irish Brigade, and the Union garrison at Lexington. Within fortifications occupied by 3,500 Federal troops, the defenders hastily dug entrenchments, built pits lined with sharpened stakes, double rows of entrenchments, artillery lunettes, and strong earthen ramparts more than ten feet high around Mulligan’s headquarters at the college building. They also stripped water pipes from the building to lay fuses for mines hidden along the easiest approaches, and their works enclosed more than fifteen acres while cleared slopes outside gave a clear view of any enemy advance. By Sept. 12th Price had reached Lexington, briefly engaged Federal troops, and then camped south of town at the fairgrounds while awaiting his ammunition train. On Sept. 18th, Price and twenty thousand State Guard troops advanced on the Union position and completely encircled the earthworks. As the Southerners pressed forward, the Federal defenders were forced back into the inner works and away from water supplies, soon exhausting the two cisterns within their lines and suffering from thirst in the oppressive late-summer heat. On the 19th both sides exchanged artillery fire, and as hot shot struck the fort, Maj. Van Horn found a cannon ball burning through the flooring of the building and threw it out with a shovel, while a teenaged private, Charles Lantheaume, took on the task of shoveling out the hot projectiles. During the battle, estimated Union losses were 40 killed and 120 wounded, while State Guard casualties among the enrolled soldiers were about 38 killed and 150 wounded, with casualties among irregular Southerners likely double that number. To the east lie five unknown Union soldiers who died in the battle; their remains were found in 1932 during excavations near the site of the old Masonic College building, which had served as Union headquarters during the siege, and equipment found with the bodies suggests they may have been part of Col. Thomas A. Marshall’s cavalry.
