Why did Nevada join the union?

Answer 1

Both joined during the war and remained as separate states after the war.

West Virginia actually seceded from the seceding state of Virginia, having opposed joining the Confederacy and following a long period of growing differences with the rest of the state due to geography. When Virginia seceded, secession was not recognized by the Union, but the government of Virginia was declared vacated by the secession act, leading the West Virginia Wheeling Convention to be recognized by the US government as the legitimate government of Virginia, who in turn voted to authorize a new state - West Virginia, to be formed and which was in turn admitted to the Union.

Nevada was set up to be a pro-Republican state in advance of the 1864 election. It was broken off of Utah territory in 1861 due to religious and political differences from the Mormon territory, and it's acceptance into the Union was pushed forward to 31 Oct 1864 to ensure votes for Lincoln and an increased Republican majority in Congress. This is also controversial because some historians doubt Nevada met the commonly accepted (though not legally binding) criteria for statehood, notably the low population (under 40,000 people at the time).

Answer 2

West Virginia was once part of Virginia. When Virginia declared secession from the United States to become part of the Confederacy, the counties in northwestern Virginia voted to secede from Virginia and remain loyal to the United States. That area of Virginia became West Virginia. West Virginia became the 35th U.S. state on June 20, 1863.

Answer 3

Nevada joined the union in 1864.