Although Sterling Price commanded about 5,000 men when he left Springfield, volunteers have streamed in from all over Missouri. By the time he lays siege on Lexington he has 10,000 to 12,000, largely farmers armed with shotguns and hunting rifles.
Colonel James Mulligan, with about 3,500 soldiers has orders to hold Lexington at all costs. He constructs elaborate defenses around the Masonic College, consisting of trenches, earthworks, sharpened steaks and clear fields of fire.
Picture is taken from The Civil War's First Blood, which I highly recommend.
He has also been promised reinforcements, which will never arrive.
As Price's advance guard approaches Lexington on September 11 they have a brief skirmish with Mulligan's defenders. By the end of the next day, Union troops have abandoned the town and are hunkered down inside their fortifications. Price settles down to wait for his main force.
Local southern sympathizers arrive daily with lunch pails, take pot shots at the hated federals in the morning and then break for the noon meal.
Meanwhile Jim Lane has regrouped and leaves Ft. Lincoln with "a smart little army of 1,500". His objective is not to pursue Price, but to loot, burn and take vengeance on Missouri.