The American Chestnut was nearly wiped out in the US due to chestnut blight introduced by imported Japanese chestnut trees. Researchers have pursued two main avenues for repopulating the American Chestnut: direct genetic modification / engineering (above link) and cross breeding with Chinese Chestnuts (blight resistant) then re-breeding the result back with American chestnuts. This is to hopefully keep it as close to American chestnuts while also gaining blight resistance.

I've never had chestnuts, even though it used to be one of Eastern Americas most populous trees. I was hoping I could get some and plant them around here and there but we aren't to the point that they're commercially available yet (though available by request)