Dozens upon dozens of forts across the south were revolutionary era structures built by the states or colonies. Others were built before the states in which they existed were acquired by the United States itself. In many cases this included the primary defensive fort for major harbors and inlets.
None of these various operations resulted in the loss of life due to the fact that these facilities were not defended, and the officials at each either resigned their employment, or in the case of military personnel, they returned north by boat or train.
Many of the properties were simply abandoned as the union army consolidated its troops from outlying posts.
Others were claimed by the states themselves for the simple reason that they had rightful ownership of the properties. Several of the coastal forts in the south dated back to the revolution and were built and paid for by the individual states, not the federal government, which acted only as conditional tenants to garrison them in defense.
That’s a nice rationale but poor excuse. It was not their property to invade and seize, no matter how the feeeeeeeel.
US Federal forts in 1860 were still Federal forts in 1861, regardless of which state or other government might claim authority.
Seizures of those forts, plus ships, arsenals & mints, etc., were generally peaceful because President Buchanan did nothing to defend them.
In Buchanan's defense, there may have been nothing he could have done, and in some places where he did, in fact, have Union troops stationed (i.e., Forts Pickens & Sumter) they usually did remain at their posts, and defended them
Texas is a different story.
But each seizure had strong effects on Northern public opinion, which waxed for war, then hoped for peace when rumors of settlement circulated.
PeaRidge: "Others were claimed by the states themselves for the simple reason that they had rightful ownership of the properties."
To repeat: those forts which belonged to the Federal government in 1860, still belonged in 1861, regardless.
Secessionist states were never said to "occupy" their own state forts, but rather to have seized Federal property.