APR 12 1861 FORT SUMTER SHELLED, BUT THE INSURRECTION AND 'WAR' STARTED EARLIER

THE SHELLING OF FORT SUMTER IN CHARLESTON HARBOR STATING AT 0430 HOURS on Apr. 12, 1861, IS VIEWED BY MOST HISTORIANS AND AMERICANS AS THE START OF THE CIVIL WAR.  However, one can make a good argument that the war actually started earlier.

Let's set aside, for now, the issue of whether secession was legal.

Assuming, for the sake or argument that secession was legal, then legally, any actions by state forces to seize federal facilities and property BEFORE their official secession are acts of insurrection and federal crimes.  The Constitution recognizes the power of  the federal government to suppress insurrections.   If, secession as carried out was unlawful then the actions of S.C. and secessionist forces were insurrections.  In fact, once the seizures began, Lincoln announced that he would take steps to reclaim federal property.  Both he and former Pres. Buchanan believed secession, at least as carried out, was unlawful. 
Some of the facilities were maintained only skeleton crews or custodians.  Others had more personnel but surrendered in the face of overwhelming opposing forces.  At that time the U.S. Army consisted of only around 16,000 personnel and most were stationed on or near the frontier.  There were no significant international threats.

Some of the major events before the shelling of Fort Sumer are listed below.

DEC. 20, 1860  South Carolina formally secedes.  Shortly thereafter, a delegation from S.C. demands that Pres. Buchanan remove all federal forces from Charleston. Buchanan refuses.  He announces that Fort Sumter will be defended by federal forces.  Earlier Buchanan announced that secession was unlawful

JAN 2 1861  South Carolina forces take control of Fort Jackson in Charleston Harbor.

JAN 3 1861, Even before the state’s official secession on Jan. 19, 1861, Georgia forces take Fort Pulaski on the Savannah River There are only two federal employees present who surrender without a fight in the face of overwhelming force.  Also seized is the U.S. arsenal at Augusta

JAN 5, 1861  Alabama seizes Fort Morgan and Fort Gaines, even before its official secession on Jan 11.

JAN 6, 1861  Even before the state’s official secession on  Jan 10, Florida forces seize the federal arsenal at Appalachicola.

JAN 7, 1861, Even before the state’s official secession on Jan 10,Fort Marion is seized by Florida forces. 

JAN 9, 1861  The unarmed supply ship Star of the West, , is fired on by secessionist forces and forced to turn back before reaching Fort Sumter in Charleston Harbor.  When the first shots were fired, the ship raised it's colors, but when the shelling continued, it retreated. Union forces in the Fort Sumter hold their fire.  S.C. refuses to allow re-supply of Fort Sumter.

The U.S. Arsenal at Baton Rouge is taken over by La. state forces prior to formal secession on Jan. 26

"Task Force Walton" disembarked the next morning at Baton Rouge. Upon going ashore, Walton's troops rendezvoused with militia units from the capital city. Thus augmented, the Louisianians, now numbering some 600 strong, proceeded to the arsenal and barracks, which they surrounded.4

At 5 P.M., two of Governor Moore's aides-de‑camp, Colonels Richard Taylor and Braxton Bragg, advanced under a flag of truce. Knocking on the gate of the arsenal, the two officers delivered to Captain Joseph A. Haskin, the commanding officer of the barracks, an ultimatum from the governor. This document read;

p403 The safety of the State of Louisiana demands that I take possession of all Government property within her limits. You are, therefore, summoned hereby to deliver up the barracks, arsenal, and public property now under your command. With the large force at my disposal this demand will be enforced. Any attempt at defense on your part will be a rash sacrifice of life.5

Anticipating no reinforcements or support, and confronted by overwhelming odds, Haskin deemed it proper, after consulting with his subordinate officers, to surrender to the state authorities.6 "

 

http://penelope.uchicago.edu/Thayer/E/Gazetteer/Places/America/United_States/Louisiana/_Texts/LH/2/4/Seizure_of_the_Forts*.html

JAN 10, 1861  Florida formally secedes

JAN 11, 1861,  Alabama formally secedes.

JAN 19, 1861,  Georgia officially secedes.

JAN 26, 1861, Louisiana officially secedes

FEB 1, 1861,   Texas formally secedes

MARCH 31, 1861  Fort Bliss, in El Paso Texas surrenders to Texas forces

APRIL 3, 1861  Secessionist forces fire on the privately owned cargo Schooner Rhoda H. Shannon in Charleston Harbor.  That ship carried ice destined for Savannah but stumbled by mistake into Charleston Harbor. S.C. forces thought the ship was send to re-supply Fort Sumter.

 

APRIL 12, 1861,

 

South Carolina demands surrender of Fort Sumter or the Fort will be shelled in one hour.

 0430 hours, Secessionist forces open fire on Fort Sumter in Charleston Harbor.  Until attacked Fort Sumter never fired on any South Caroline targets.

See this article on pre-secession seizures in Louisiana. 
http://penelope.uchicago.edu/Thayer/E/Gazetteer/Places/America/United_States/Louisiana/_Texts/LH/2/4/Seizure_of_the_Forts*.html

See this article from  Wikipedia on other seizures and dates.  https://en.wikipedia.org/wiki/Timeline_of_events_leading_to_the_American_Civil_War#1860_election.2C_November_6.2C_1860_to_fall_of_Fort_Sumter.2C_April_14.2C_1861