West Virginia became a state following the Wheeling Conventions of 1861, at the start of the American Civil War. Delegates from the Unionist counties of northwestern Virginia decided to break away from Virginia, which also included secessionist counties in the new state. West Virginia was admitted to the Union on June 20, 1863, and was a key border state during the war. It was the only state to form by separating from a Confederate state, the first to separate from any state since Maine separated from Massachusetts, and was one of two states admitted to the Union during the American Civil War (the other being Nevada). While a portion of its residents held slaves, most of the residents were yeoman farmers, and the delegates provided for gradual abolition of slavery in the new state Constitution.