The primary settlers of Audrain County immigrated from areas in Tennessee, Kentucky, and Virginia. With most of these people being farmers, the development of the merchant community was limited in the early years. It wasn’t until the introduction of the North Missouri Rail Road lines, the economy and population boomed. From 1850 to 1860, the white and freed population in the county nearly doubled and the slave population nearly tripled.
At the outbreak of the war, the inhabitants were split almost in half in their loyalties; around 500 men signed on for the Confederacy’s cause and 600 pledged themselves into service to the Union.
Federal occupation of Mexico was swift. Due to the rail line, their interest in the area is no great surprise. While no official battles are documented, guerrilla warfare and skirmishes took place as the two sides in the Civil War fought for control of pieces of Missouri, attempting to gain control over the whole state. On July 15, 1861 there was a skirmish in Mexico involving Missouri’s 2nd infantry. The next day, at Martinsburg, was another skirmish, this time engaging Missouri’s 1st Reserve Corps. On the very next day, July 18, 1861, was yet another skirmish with Missouri’s Reserve Corps (Company A.)