Militarly, Mexico was important because of the railroad. Railroads were vital methods of transportation for manpower and material during the war. The North Missouri Railroad ran from St. Charles, MO. to Mexico and then on to Macon, MO where it joined the Hannibal and St. Joseph railroads. The only line that crossed the entire breadth of the State. Both sides recognized the strategic benefits of controlling this part of NE Missouri.
Early in the war several Union army units were sent across from Illinois to help secure the State for the Union. One of the units was the 21st IL. Infantry commanded by Colonel Ulysses S. Grant, who camped here in Mexico from July 20 to August 7, 1861. While in this area Col. Grant visited Graceland Mansion which was buildt in 1857 by John P. Clark. Now listed on the registry of historic places, and hosted by the Audrain Historical Society.
The antibellum mansion is open for tours of house and grounds if interested.