How rare is Butternut?

[IndyIan]

I just learned what Butternut looks like and discovered that we have 4 together in a fence row.  I've done some reading that butternut canker has or will kill about 80% of the trees.

I'm up near the northern limit for them and don't see many at all but I was wondering about how common they are in the US?

Here is a site that a fellow from Ottawa, ON has put up to promote planting of them.
  http://cobjon.com/butternut.html

I've decided to plant as many nuts as I can from my trees in a low well drained area close to the parent trees.  Sort of a butternut nursery.  

Anyone have any tips for planting?

Thanks,
Ian