The paper cited below estimates that 1.8M hectares burned annually in California before 1800 (over 4M acres). [1] That's about how much burned in 2020. [2]

[1] https://nature.berkeley.edu/stephenslab/wp-content/uploads/2...

[2] https://en.wikipedia.org/wiki/2020_California_wildfires

Edit: clarity

I'm wondering what type of fires these were. There is a vast difference between a forest crown wild fire, and a cooler one that mostly works burning undergrowth and leaf litter. Still fires, still covering the same amount of ground, one can destroy the forest and anything else in the vicinity, the other can help plants germinate and seeds the forest for the next period of growth.

You only get high intensity fires if you have too LITTLE fire, not too much. If you have annual burning it's not going to be high intensity.

That said, even high intensity fires have pretty impressive recovery. Do you want to give me a high intensity fire from 5+ years ago? I can then show you the recovery if you want.

They were low intensity fires. Many areas burned every 3 years on average before 1850. These same areas haven't experienced a fire since 1900

Someone already linked to the paper - but the eyewitness statements give a good example of just the extent and regularity of fires:

An eye-witness account of smoke in northern California forests (C.H. Merriam 1898, quoted in Morford, 1993) reported ‘‘Of the hundreds of persons who visit the Pacific slope in California every summer to see the mountains, few see more than the immediate foreground and a haze of smoke which even the strongest glass is unable to penetrate.’’ C.H. Merriam traveled extensively in California and was Chief, Division of Biological Survey for the US.

I've seen estimates of everything burned every 5 years which I found credible.

Or this on use by native americans

“Fire was a constant companion, a kind of universal catalyst and technology,” says Stephen Pyne, an emeritus professor at Arizona State University, author and fire historian.

Yosemite itself was routinely burned to clear underbrush, open pasture lands, provide nutrient-rich forage for deer, and to support the growth of woodland food crops to feed and sustain what was once a large and thriving indigenous population.

https://www.history.com/news/native-american-wildfires

A lot of the hot takes about the amount of fire we have no ignore the real issue - too little fire in landscapes that historically were shaped (and need) fire. And no - fire does not destroy nature - though I've seen some Instagram posts of folks rushing into burned areas to get clicks and good shots. Seriously - come back in 1-2 years and be amazed in many cases.

Fire was 101 land management "technology" and indigenous populations used it over literally thousands of years to improve their environment.