1900 Galveston hurricane
The Great Galveston hurricane made landfall on September 9, 1900, near Galveston, Texas. It had estimated winds of at landfall, making the cyclone a Category 4 storm on the modern day Saffir–Simpson Hurricane Scale.
The hurricane caused great loss of life, with a death toll of between 6,000 and 12,000 people; the number most cited in official reports is 8,000, giving the storm the third-highest number of deaths or injuries of all Atlantic hurricanes, after the Great Hurricane of 1780 and Hurricane Mitch in 1998. The Galveston Hurricane of 1900 is the deadliest natural disaster to strike the United States. This loss of life can be attributed to the fact that officials for the Weather Bureau in Galveston brushed off the reports because the city had "weathered them all" and they did not realize the threat. The second-deadliest storm to strike the United States, the San Ciriaco hurricane of 1899, caused around 3,400 deaths.
2005 Atlantic hurricane season
Hurricane Katrina formed in mid-August over the Bahamas. It became a tropical storm on August 24 and reached hurricane intensity before making landfall in south Florida as a minimal hurricane. A few hours later, the storm entered the Gulf of Mexico and intensified rapidly into a Category 5 hurricane while crossing the Loop Current on August 28. Katrina made landfall shortly after 06:00 CST on August 29 near the mouth of the Mississippi River as an extremely large Category 3 hurricane. Category 5-level storm surges (as the storm had weakened only in the previous several hours) caused catastrophic damage along the coastlines of Louisiana, Mississippi, and Alabama. Within hours, levees separating Lake Pontchartrain from New Orleans, Louisiana were breached by the surge, ultimately flooding about 80% of the city. Wind damage was reported well inland, impeding relief efforts. Katrina is estimated to be responsible for at least $125 billion (2005 USD) in damage, breaking Hurricane Andrew's record in 1992 and making it the costliest natural disaster in U.S. history until Harvey tied it in 2017. It was the deadliest U.S. hurricane since the 1928 Okeechobee Hurricane, killing at least 1,836 people. The 1900 Galveston Hurricane remains the deadliest natural disaster in United States history, with a death toll of approximately 6,000.