I was looking at the California Wildfire History Map (https://projects.capradio.org/california-fire-history/#9.62/...) a while back and remember noting that the CZU fire was the first recorded burn for most of the affected area.

I am not sure how complete the map is, but I suspect that the GP means the fires (such as the 1985 Lexington fire) further east mapped in red? Of those, I think I only see two meaningfully overlapped by newer fires (2009 and 2016 Loma fires overlapping 1985 Lexington, 2020 Park within the footprint of the 1985 Finley fire).

Edit: looks like the Finley/Park fires are technically just east of the mountain range, at least per http://www.scmbc.org/map-of-bioregion.