On June 3, 1861, Stephen A. Douglas, Lincoln’s opponent in the 1860 presidential campaign, died of typhoid fever.
On that same day, the first land engagement between the Union and the Confederacy was fought, called the Battle of Philippi. A relatively bloodless encounter, Union General George B. McClellan sent several regiments to attempt a double envelopment of a Confederate force at Philippi, Virginia (eventually West Virginia). The attack was prematurely launched with a pistol shot by a Southern sympathizer, a mother who had sent her son to warn the Confederates, saw her son captured by Union troops. The attack was started before the Union troops were completely in place, which gave the Southerners a chance to flee, which they did, most in their bedclothes. The battle, more of a race really, launched the short Civil War career of McClellan, who was eventually named to command the Army of the Potomac.
On June 8th, Tennessee voters decided to secede from the Union. The vote margin was better than 2-to-1. Also that day, the Commonwealth of Virginia turned their troops over to the CSA.
June 10th saw the Battle of Big Bethel. A larger affair than Phillippi, The Union attacked Confederate outposts near the present-day village of Tabb, Virginia. Initially successful, the Union troops were eventually repulsed.
On June 11th, the Second Wheeling Convention met. This gathering would eventually result in the secession of the new state of West Virginia from the Confederate Virginia. Three days later, Confederate General Joe Johnston began his withdrawal from Harpers Ferry, blowing up the 800-foot railroad bridge over the Potomac.
Missouri Governor Claiborne Jackson called for 50,000 volunteers to keep the Union from taking over Missouri
Also in Missouri on June 17th, Nathaniel Lyons captured the strategic river port of Boonville.
On the 21st, the North Carolina Secession Convention unfurled a new flag, reflecting their status as a Confederate state.
On June 23rd, despite desperate attempts by the Union to protect the Baltimore & Ohio railroad, General Thomas “Stonewall” Jackson attacked the rail center at Martinsburg, VA, destroying 42 locomotives and almost 400 railcars.
June 27th saw the first significant naval action, the Battle of Mathias Point. The Union Navy established a blockade to deny Chesapeake Bay to the rebels, while the Southerners in turn, were trying to keep the Union out of the river systems, particularly the Potomac by establishing a battery of artillery at Mathias Point, which would effectively block access to the Potomac. The Union attacked, landing Marines to destroy the battery, but the Confederates counter-attacked, driving the Union forces back to their ship. The death of the Union commander, James H. Ward, unsettled the Union crews, which ended the battle.
Three days later, on the 30th, The CSS Sumter slipped through the Union blockade of USS Brooklyn, making it to the open sea.