Currently limited to the part of the US that's east of the Mississippi.
The entire natural range of the American chestnut was east of the Mississippi.
Unfortunate that most of HN's reader base is in CA.
Source?
I doubt that is true anymore. Maybe 1/3?
There are several stands of genetically-pure American chestnut on the West Coast that remain because they were isolated from the blight. These were trees imported by settlers and arborists in the 19th century—they should remain protected!