The war was all about slavery. States and even families were divided on which side to fight for based on their beliefs about slavery.

West Virginia was not a profitable place for slave owners to apply their slave labour. It didn't have the climate, topography and soil to grow cotton or tobacco as the eastern part did. Therefore there was much less slavery.

As an old state near the commerce of the North, a lot of whites settled there, even moving from the North, finding they could compete and labour in profit against slave plantations with much higher productivity.

Thus, a huge portion of the western state was free rather than enslaved.

Fredrick Law Olmstead wrote much on those topics above. He showed all sorts of evidence that slavery was impoverishing the vast majority of whites in Virginia rather enriching them. He interviewed hundreds of Southerns on the topic of slavery and wrote a few books. "Journeys and Explainations in a cotton kingdom" is fantastic book on the subject.

So, in summary, it was in the interest of West Virginians to stay loyal and help end slavery.

Much has been written and recorded where there was a question whether Virginia would secede along with the Deep South or stay in the Union.

Check out this letter which the editor of the Charleston Mercury (one of the main "Fire Eaters") wrote in 1861 to try to block the inclusion of a ban on slave trade in the new Confederate Constitution.

In summary, it states that slavery is core to the revolution and what it means to be confederate state. It is the only thing that binds them together. The risk to slavery isn't the ratio of whites to slaves but the ratio of slave owning wealthy whites to "unfixed" whites who in "excess" and "unfixed in the social compound." He argues that it is critical to keep importing slaves so that many whites own slaves and thus keep the institution running. He writes that there will be another similar revolution of free vs slave if there aren't enough slaves to go around.

http://docsouth.unc.edu/imls/secession/secession.html

A key paragraph: "But it may be that to this end another revolution may be necessary. It is to be apprehended that this contest between democracy and slavery is not yet over. It is certain that both forms of society exist within the limits of the Southern States; both are distinctly developed within the limits of Virginia; and there, whether we perceive the fact or not, the war already rages. In that State there are about 500,000 slaves to about 1,000,000 whites; and as at least as many slaves as masters are necessary to the constitution of slave society, about 500,000 of the white population are in legitimate relation to the slaves, and the rest are in excess. Like an excess of alkali or acid in chemical experiments, they are unfixed in the social compound. Without legitimate connection with the slave, they are in competition with him. They constitute not a part of slave society but a democratic society. In so far as there is this connection, the State is slave; is so far as there is not, it is democratic; and as States speak only from their social condition, as interests, not intellect, determine their political action, it is thus that Virginia has been undecided--that she does not truly know whether she is of the North or South in this great movement. Her people are individually noble, brave, and patriotic, and they will strike for the South in resistance to physical aggresion; but her political action is, at present, paralyzed by this unnatural contest, and as causes of disintegration may continue--must continue, if the slave trade be not re-opened--as there will still be a market at the South for her slaves -- as there will still be pauper labor from abroad to supply their places, and more abundant from industrial dissolutions at the North, and the one race must increase as the other is diminished--it is to be feared that there the slave must ultimately fail, and that this great State must lose the institution and bend her proud spirit to the yoke of another democratic triumph. In Maryland, Missouri, Kentucky, and even Tennesse, and North Carolina, the same facts exist with chances of the like result."