A Recent news event (Pioneer Cabin Tree in California felled by storms), brought drive through trees to mind. When I looked at the pictures, I realized it is not the same tree I drove through last time I was in the Redwood Forest.
Searching found some different answers. This one by the US forest service and this one by a commercial site. Both seem to be subject to some bias, The commercial site lists more, but not sure it is exhaustive.
How many trees (singular) are there in California you can drive through, as of January 9, 2017?