On Wednesday, April 17, 1861, the Virginia state convention passed an ordinance of secession 88 to 55. The ordinance would not be official until a majority of voters ratified it in a statewide referendum on May 23, but there was no chance this would not happen. Virginia was, for all intents and purposes, out of the Union.
The loss of Virginia was a big blow to the Union as historian Bruce Catton explains, "Without Virginia the Southern Confederacy could not have hoped to win its war for independence; with Virginia the Confederacy's hopes were not half bad, and they would get even better when people realized that Virginia would come equipped with Robert E. Lee. American history has known few events more momentous than the secession of Virginia, which turned what set out to be the simple suppression of a rebellion into a four-year cataclysm that shook America to the profoundest depths of its being."
Virginia state troops were already on the way to Harper's Ferry to seize the U.S. Arsenal there.
Also on this date, Confederate President Jefferson Davis issued a proclamation "inviting all those who may desire, by service in private armed vessels on the high seas, to aid this government in resisting so wanton and wicked an aggression, to make application for commissions or letters of marque and reprisal to be issued under the seal of these Confederate States."
This was either a noble calling combining patriotism and profit or piracy, depending on your point of view. Later, the Union would charge the officers and crew of the Savannah with piracy, claiming that their Letter of Marque was invalid since the Confederacy was not a sovereign nation. Davis threatened to hang a Union officer for each executed Confederate privateer. Thereafter, the Union treated privateers honorably as prisoners of war.
At Galveston, Texas, the Star of the West, which had tried unsuccessfully in January to reinforce and resupply the garrison at Fort Sumter, was captured by Confederate troops.