Which state was formed when five of the northern counties in virginia decided not to secede from the union?

West Virginia is your answer

West Virginia was formed after Virginia seceded, for the 5 counties did not want to leave the Union. They were given states-rights,  and was admitted to the Union.

~Rise Above the Ordinary

on april 6, 1917, the u.s. joined its allies--britain, france, and russia--to fight in world war i. under the command of major general john j. pershing, more than 2 million u.s. soldiers fought on battlefields in france.