It seems that every year, wildfires threaten western states such as are now blazing in California.
(A) What happened 200 years ago. Surely lightning would set occasional fires. Did California and Arizona simply burn before the advent of fire fighting?
(B) I realize that we on the east coast get more rain than Arizona, but are there every wildfires of that magnitude east of the Mississippi River?
Regarding A: Yeah, there were some big burns in the past:
Which led to a “fight 'em as soon as we can” policy. Which then caused ecological issues. Basically, we’ve come to learn that frequent human intervention (fighting wildfires all the time) leads to a buildup of excess fuel – twigs and such that build up over time – that eventually leads to huge, catastrophic burns. Without such human intervention, fires do happen, but they exhaust the fuel supply somewhat quickly and then new growth recovers. Some vegetation species are adapted to survive these fires, and some are even adapted to thrive in them in that their seeds don’t sprout until after a good fire when all the competition is burned and there’s new soil for them to start in.
So nowadays, I think they try to control the amount of burning near properties and such, but otherwise try to let small fires run a reasonable course and they occasionally even prescribe fires to preemptively burn out excess fuel.
Settlers in the past (Native Americans and later immigrants) also burned woodlands to make meadows and croplands, and these gave rise to their own niche ecosystems.
As for B: Not sure, but Wikipedia has a list:
In the East prior to the Age of Columbus the natives here constantly burned the woodlands. The very 1st Europeans to arrive commented in their journals that the woods here were like the parks back in Europe.
The idea that we allow the forest to grow untouched is a recent concept of the last 100 years or so.
People say california doesent have seasons, we do. Flood, mud, fire, and earthquake. plenty of fires are left to burn, sometimes for weeks because they are so far out in the middle of nowhere that there is little point trying, especially when no homes are threatened.
Those are the trickiest ones to fight. 
A temperate rainforest seems like the worst place to look for evidence of fire, but the signs in Olympic National Park in Washington say that the area now covered in giant 400-year-old trees draped in moss took its shape from a massive fire that burned over the district 400 years ago, allowing all this present-day growth to emerge.
Wile E. Fires, Super Conflagration
Most of the West is a fire ecology, fires are natural here, and plants have evolved to survive or even take advantage of them. Also, for the past 3000 years or so humans have used fires for their own purposes here and elsewhere.
With climate change and the drying/heating of much of the area (apparently the PNW will not, at least short term), we’ll see a lot more fires. The suppression of fires over time creates fuel build up that ensures that when we do get fires they will be hotter and much harder to control. Because people commonly build in steep, dry, areas difficult to protect (fires race up hills and kind of explode at the ridge crest, then burn slowly down hill), these fires are very destructive to property. The town of Weed up in the Mt.Shasta area just burned practically to the ground this week. We’ll be seeing more of this.
In addition to what has been stated, the west has had explosive growth and development in recent years. Neighborhoods and housing has encroached into previously uninhabited areas and are built right next to wild lands. There is a concerted effort on the part of firefighters to protect property and buildings - with more development in the forest, there will be more firefighting activity now as well. Where previously they may have let it burn out on it’s own. More firefighting = less natural reduction in undergrowth and fuel = more explosive and hard to manage wildfires right near developments.
It’s interesting to note the enormous King fire east of Sacramento has burned 70K+ acres in about a week, but no structures have been lost to this point, and no casualties, thankfully. Big fires start grabbing headlines when there are big losses to property.
To segue slightly off of this you actually see commercials and billboards about “creating a defensible space” around homes in wooded areas. They want as much as 100’ cleared of any heavy vegetation around structures, creating a natural firebreak as well as giving fire crews enough room to work. They on man occasions will not even try to protect a structure where this has not been done depending on the resources available.
While this doesn’t exactly answer the question, it’s worth noting that in my own experience with wildfires (both forest and range fires in the western states), the hottest, fiercest fire I ever experienced was in the east… in metropolitan Boston, to be exact. Burning in a 1000+ acre marsh along the Neponset River. There were many feet of semi-decayed swamp vegetation on the ground with standing tules and brush to about 8 ft. high. The wall of flame when that lot got going was awsome. There must be, or have been, enormous fires in the southeastern swamps and the Everglades.
Wait earthquakes have a season? I thought they just fit themselves in whenever.
Heh. Ain’t no seasons 5 miles down.
California does have seasons. It’s a mediterranean climate, which is a small and rare type that mainly exists on the west edges of continents. The reason people don’t think it has seasons is that the seasons are about water, not temperature. Artificial irrigation blurs that. You’d sure know what the seasons were if you didn’t have a hose.
Some people divide it into three seasons, dormant/dry (early summer to late fall), winter/wet (late fall to spring), and growing season (spring to early summer). The only time wet and sun coincide is in the last one, so that’s when the native plants get their grow on. The climate reaches from nearly Mexico at least through Oregon, so there is quite a difference in the length and intensity of each season. But always, almost all the rain is winter rain, and the summers are close to rainless, even in Oregon. You might get 6 inches in San Diego and 80 inches in Humboldt, but it all falls in winter.
Which is why this is a fire ecology.
Forest have to be harvested or they burn.
Thank the Tree Hugger’s for many many fires.
When hunting the Yampa Colorado area, the big reservoir area to be exact.
For every live standing tree there had to be 2-3 dead standing trees and that or more crisis-crossed on the ground. The dead trees don’t decompose unless they are on the ground and then very slowly because of the lac of moisture.
Needles are 12 or more inches deep in the duff!
The place has to burn!!!
This message brought to you by by International Timber Industries Lobbying Group.
Harvesting in a reasonable way does practically nothing to affect wildfires. What little fuel is removed in terms of logs is countered by the large amount of limbs, bark and sawdust left around on the ground which dry out and are a fire enhancer. Especially since they are all cut at the same time. Clear cutting does work, but IMHO that’s bad on its own and not justifiable for fire suppression purposes. (It would basically come down to: “Prevent Forest Fires: Get Rid of Forests.”)
“Clearing out dead trees …” is also a non starter for lumbering. Timber cutters have no interest in dead trees. The wood isn’t worth taking out of the forest.
Before humans, fires were frequent and limited. Small patches would burn until they hit the areas that had burned recently. The buildup of fuel in one area was fairly small. Many, many species of plants rely on these mild burns to advance their life cycle in one way or another. Significantly reducing fires by any means is really bad for the ecosystem the forest needs to stay healthy.
I thought it was a failed haiku.
I don’t know how true this is in other regions, but one of the interesting things I learned in a forestry class I took that dealt specifically with the Northern Rockies is that the burn intervals in forests prior to European settlement were largely dependent on the amount of human activity in the area. Forests along major transportation routes would have very frequent burn intervals (like as few as 10 years) whereas the forests in otherwise identical tributary valleys (i.e. ones that don’t go anywhere) would have burn intervals more on the order of 75-100 years. That latter number is more what you’d expect for lightning strikes. There’s some disagreement as to what extent this reflects intentional land management or simply accidental starts, but humans being the most common cause of wildfires is not a new development.
The modern implications of this are that of course European settlement followed the same geographic constraints as Native settlement, and so most modern towns and cities in the region are in areas where the forests are adapted to frequent low-intensity fires. That’s where you get the situations where now, a century of active fire suppression later, you’ve got tinderboxes with potential for huge conflagrations. For forests in Wilderness Areas and other out-of-the-way places, the Forest Service has more or less adopted a “let 'em burn” policy. Even though those forests mostly haven’t had a fire in recorded history either, because they are adapted to 75-100 year fire intervals they generally don’t have the same fuel accumulation problems and they generally don’t get out of hand when left alone.
Well someone isn’t aware of the extent of forest harvesting that is going on today.
In some areas every branch is processed for bio-mass. The power company’s are consuming thousands of tons of bio-mass and that leaves the forest floor bare. There isn’t a bush for a rabbit to hide behind after the harvesting is done and then the new growth is spayed with herbicides and then a couple years later the plot is planted with red or white pine. Nothing for wildlife anymore 
I think this depends on the region and on who owns the forest. The NFS stands in the more remote areas of the Pacific Northwest (which is a lot of them) are a mess after clearcutting. Just getting the logs out is a major job, never mind the rest.
I can imagine private forests in relatively flat areas in, say, the SE, are “mowed and bagged”.
Incidentally, the big Rim fire from last year, near Yosemite, has caused squabbling now between logging interests and environmentalists. The loggers want to get in there and harvest the trees recently killed, but still standing, as salvage. Those opposed to this say the addition of logging roads and infrastructure will permanently change the forest and make it more accessible for future development.
It does make me wonder about logging techniques that can be used to reduce the risk of major fires now. Is artificial fire suppression causing issues with too much fuel building up, necessitating the need for artificial means to reduce said fuel buildup?