What’s the biggest disaster to hit the United States? It’s not Hurricane Helene. It’s not Hurricane Harvey. It’s not Hurricane Katrina. It’s not even the hurricane that hit Galveston. It was the American Civil War. Nothing else damaged America that badly.
I’ve also read that, adjusted for inflation, the Civil War has a much higher damage cost than the costliest of natural disasters (if you combine Katrina’s adjusted cost and Harvey’s adjusted cost, you still won’t reach the adjusted cost for the biggest fight over slavery).