The significant event that occurred on April 15, 1861, following the battle was Lincoln's call for volunteers.

On April 15, 1861, in the aftermath of the Battle of Fort Sumter, President Abraham Lincoln made a crucial announcement calling for 75,000 volunteers to join the Union Army. This significant declaration was a direct response to the Confederate assault on Fort Sumter, which signified the official beginning of the Civil War. Lincoln's appeal sought to strengthen the Union's military forces as tensions between the North and South intensified. The response was remarkable, with citizens from numerous states eager to enlist and support the Union. This surge of volunteers played a vital role in shaping the early phases of the war, underscoring the urgency and gravity of the impending conflict.