20th Century Service and Reorganization

First Kentucky Regiment, National Guard served during Pershing's Mexican Border Expedition, 1915.

 After their participation in the Spanish American War, the Legion continued their service to the commonwealth as they had in the 19^th century, both at home and abroad. During this time, significant changes were being made by the federal government regarding state militias, an after effect of the Spanish American War. If the United States were to continue international military intervention, the military needed to be regulated on a federal level. In 1903 and 1912, major federal laws came into effect that restructured state militias. The Legion was restructured into the Kentucky Army National Guard and was given the designation of the 138^th Field Artillery. The 138^th Field Artillery served during World War I, World War II, and the Vietnam War. Headquarters XXIII Corps Artillery and 138^th Field Artillery, headquartered at the National Guard Armory in Lexington, Kentucky, both trace their roots back to the Louisville Legion.