Final answer:
Following the attack on Fort Sumter, President Abraham Lincoln called for 75,000 volunteers and established a naval blockade, leading to the official start of the American Civil War and the secession of more states.
Step-by-step explanation:
After the fall of Fort Sumter on April 15, 1861, President Abraham Lincoln took decisive action to address the burgeoning conflict between the North and the South. In response to the Confederate attack, he called for seventy-five thousand volunteers from state militias to bolster the Union forces. Not anticipating the fervent response, the number of troops from Northern states quickly exceeded his request.
Alongside mustering the military, Lincoln implemented a strategic naval blockade of Southern ports. This move, although indirectly acknowledging the Confederacy, worked as a mechanism to restrict their trade, particularly with European entities like Britain and France, who were keen on Southern cotton yet mindful of the conflict. Lincoln's initiatives did not go unanswered—the Confederacy saw the blockade as an act of war and officially proclaimed a state of conflict with the United States, cementing the start of the American Civil War.
Notably, the effect of Lincoln's call for troops was immediate and significant in the political landscape of the remaining states. Virginian legislators, once hesitant, voted to secede within days of his announcement, followed by other states like Arkansas, Tennessee, and North Carolina. Confederate forces attacked Fort Sumter before the Union could resupply, and the confrontation at the fort set the stage for the full-scale war that ensued, shifting the nation's narrative from one of tense standoff to overt civil strife.