Which state separated from Virginia due to its anti-slavery sentiments and remained loyal to the Union?

West Virginia separated from Virginia largely due to its anti-slavery sentiments and its desire to remain loyal to the Union during the Civil War. In the context of the 1860s, western Virginia was less reliant on slavery compared to the more agrarian and slaveholding eastern region of Virginia. As tensions escalated leading to the Civil War, the western counties felt increasingly alienated from the southern state's leadership, which favored the Confederacy.

This strife culminated in June 1861 when the northwestern counties of Virginia held a convention to establish their own government that was loyal to the Union. By October 1861, they successfully became a separate state, officially recognized as West Virginia by Congress in 1863. This was significant because it was the only state created out of another state during the Civil War and exemplified the divisions within Virginia regarding the issue of slavery and loyalty to the Union.