Why is WV on aluminum cans?

I have a question that’s been bugging me for a while now. Why is there a little map of West Virginia with a number “1” in it on the top of all soda cans?

Just two weeks ago J. Noble asked this same question in West Virginia on cola, but the discussion died out before we ever got a definitive answer. However, according to Soft Drink Excise Taxes,

I like the ones that specify a redemption amount best.
I think it’s “MICH 10¢” in Michigan, but only the ambiguous “CA Cash Refund” in California, I suppose because they offer so little back it’s not worth picking them up, which was the whole point of the deposit.

In CA it is a 5 cent refund, like just about any other place. And, I’ve made ends meet many months (when I had a lot of extra time) by cashing in coupons and recycling cans and newspapers – it all adds up faster than you think.