Complex sentence: On May 15, Louisville became a mustering out center for troops from Midwestern and Western states and on June 4,1865, military authorities established the headquarters of the Union Armies of the West in Louisville.
Split into simpler sentences: On May 15, Louisville became a mustering out center for troops from Midwestern and Western states. On June 4,1865, military authorities established the headquarters of the Union Armies of the West in Louisville.