The American Civil War

The American Civil War was fought over the Lincoln administration's determination to prevent secession and make the Confederate States of America (CSA) pay the Union tariff on their foreign trade, 40% versus 10% CSA..
Fort Sumter was blockaded because the Union tariff officials had fled there after confederate militia had prevented them from collecting taxes.
Seven southern states had seceded and formed the Confederacy (CSA) over 5 months without conflict, but an invading relief fleet sailed from NYC with troops and provisions for Ft. Sumter before it was bombarded which forced its surrender.

Five slave states did not secede and stayed in the Union without molestation and were excluded from the Emancipation Proclamation.
The Union was a slave holding nation throughout the ACW.

Union slaves were freed in December 1865 by the 13th Amendment... long after all confederate armies were surrendered and state capitols occupied by Union troops. CSA General Stand Watie surrendered the last confederate forces in June 1865.

"Every man should endeavor to understand the meaning of subjugation before it is too late... It means the history of this heroic struggle will be written by the enemy; that our youth will be trained by Northern schoolteachers; will learn from Northern school books their version of the war; will be impressed by the influences of history and education to regard our gallant dead as traitors, and our maimed veterans as fit objects for derision...
It is said slavery is all we are fighting for, and if we give it up we give up all.
Even if this were true, which we deny, slavery is not all our enemies are fighting for. It is merely the pretense to establish sectional superiority and a more centralized form of government, and to deprive us of our rights and liberties."
--- Maj. General Patrick R. Cleburne, CSA, January 1864