There are just a handful of locations in the US where they can be found at very high elevations and in very arid conditions. Some of these trees have been known to have for over 4500 years and some dead wood which decays very slowly has been tring ring dated back to over 7500 years ago. Trees that have been dead for 300+ years may still be standing.

BTW these trees are at two seperate locations several hundred miles apart.