President Lincoln's 75,000 volunteers were the militia of the loyal U.S. states called up on April 15, 1861 following the attack on Fort Sumter by the forces of the Confederate States of America. This was the beginning the American Civil War. President Lincoln called for 75,000 volunteers for a period of 90 days. These limits were established by laws that had been passed in the late eighteenth century and were not necessarily a reflection of the number of troops or the amount of time Lincoln actually thought it would take to put down the rebellion. 