According to lasdontrailofhonor.com:

As you continue on the trail, you will come upon the bust dedicated to the American Civil War. The bust is of an old Union serviceman, one of many who fought during the bloodiest war fought on American soil. The serviceman wears a signature forage cap, a fatigue hat that became the common headgear for Union soldiers. This gruesome conflict began over whether each individual state should be allowed to make their own rules or if they should follow regulation from the federal government. The southern states wanted to be able to create their own laws, and forcibly seceded from the Union in 1861. After the Confederate states attacked Fort Sumter in Charleston, South Carolina, war erupted between the Confederacy and the Union, forcing many Americans to face one another on the battle field until General Lee surrendered his troops in 1865.