[jeffersondem]

“At the time of West Virginia's admission, it's constitution required gradual abolition, as was done in other northern States.”

So it was Lincoln that added a slave state to the U.S. after the Emancipation Proclamation. That is not the answer I would have expected from a president that was “fighting to free the slaves.”

The slaves in the southern states, generally speaking, were freed immediately upon coming under control of Union forces; but slaves under control of Union forces in Union states were not freed, even though it is said Lincoln was “fighting to free the slaves.” The North continued to cling to slavery.

Perhaps there were economic and political considerations that overrode the oft-stated northern moral imperatives.

[BroJoeK]

jeffersondem: "Perhaps there were economic and political considerations that overrode the oft-stated northern moral imperatives."

West Virginia was admitted to the Union in 1863 as a gradual abolition state, using similar procedures as other northern States had previously.
In February 1865 West Virginians changed that to full, immediate and uncompensated abolition.
Iirc, they were one of only three Southern States to voluntarily abolish slavery on their own.