The State of Florida withdrew from the Union on January 10, 1861 – three days afterward a US Army captain moved his troops into the nearly-complete Fort Zachary Taylor at Key West, a fortress built specifically to protect the city and State from invasion.
Though then-President James Buchanan admitted no authority to wage war against a State — which was the very definition of treason in Article III, Section 3 – his actions with regard to reinforcing US forts were viewed as hostile and intended to precipitate a conflict.
*The economic reality of an industrial North seeking protectionist tariffs and an agricultural South seeking the opposite would eventually lead to separation. A local newspaper had editorialized its concern over Northern sectionalism in 1832 during the heat of the discussion over the National Tariff Act of that year. It read:
*My G, G Grandfather - Tariff Must Be Reduced
“We have always thought that the value of the union consisted in affording equal rights and equal protection to every citizen; when, therefore, its objects are so perverted as to become a means of impoverishment to one section, whilst it aggrandizes another, when it becomes necessary to sacrifice one portion of the States for the good of the rest, the Union has lost its value to us; and we are bound, by a recurrence to first principles, to maintain our rights and defend our lives and property.”
www.Circa1865.org The Great American Political Divide
Targeting Key West Civilians
“Construction of Fort [Zachary] Taylor [at Key West] was nearly complete when Florida seceded from the Union. On the night of January 13, 1861, Capt. [John] Brannan marched his  men from the barracks to Fort Taylor – taking possession of the fort while the city slept.
While the majority of the citizenry was for the Confederacy, there were some Union supporters on the island. Throughout the war, pro-Union supporters, white and black, tattled on the doings of their pro-Confederate neighbors, but island life in general remained calm.
One incident in February 1863, however, united all the residents against the Union army. The commander of the fort was ordered to round up “all persons who have husbands, brothers or sons in Rebel employment, and all other persons who have at any time declined to take the oath of allegiance, or who have uttered a single disloyal word, in order that they may all be placed within the Rebel lines.”
Six hundred citizens, including some staunch Union supporters whose sons had joined the Confederate army, fell into these categories. They were ordered to pack up and board ships that would take them to Hilton Head, S.C. According to one citizen:
“. . . The town has been in the utmost state of excitement. Men sacrificing their property, selling off their all, getting ready to be shipped off; women and children crying at the thought of being sent off among the Rebels. It was impossible for any good citizen to remain quiet and unconcerned at such a time.”
At the last moment, orders arrived superseding the operation. The protests of the “good citizens” had been heard.”
(Key West, Images of the Past, Joan & Wright Langley, Belland & Swift Publishers, 1982, excerpts pp. 20-21)