IStock Photo 10819049 © dmitry_7

The year of 1803, which saw the US double in size, also saw it enact its first disaster relief. On the day after Christmas, 1802, the town of Portsmouth, NH, experienced a horrendous fire that damaged much of the town. Congress later passed what is now called the Congressional Act of 1803, which offered relief by “suspend[ing] for months, the collection of bonds due to the United States by the merchants of Portsmouth.” Thus, what would eventually become FEMA, the Federal Emergency Management Agency, was born.

Today, any natural or man-made disaster deemed too big to handle by local or state authorities may be declared a US federal disaster. A state’s governor, after taking appropriate emergency action, typically submits a request for aid (and a "preliminary damage assessment") to the president. Under the Disaster Relief Act of 1974, the president may then declare a federal disaster, after which FEMA sends financial aid and emergency workers to the disaster zone.

A "disaster" can be anything, really—any event that destroys property and endangers lives. The most common is flooding—the odds a federally declared disaster (hereafter just "disaster") is a flood are 1 in 2.5. In 2008 alone, 52 disasters involved flooding. Going hand in hand with flooding are severe storms: the odds a disaster is a severe storm are 1 in 2.87.

While hurricanes are typically some of the highest-profile disasters, they account for fewer declarations than one might think. While 1 in 7.77 declared disasters is a tornado, only 1 in 10.26 is a hurricane or tropical storm. (Typhoons, the Pacific’s equivalent of the hurricane, are even rarer—only 1 in 54.12. Most typhoons recorded by FEMA involved American territories in the Pacific, like Guam, the Marianas Islands, American Samoa, etc. Only one typhoon, Iwa, hit Hawaii in 1982.) Rarer still, droughts account for only 1 in 60 disasters; and earthquakes, 1 in 115.

According to FEMA, only 7 disaster declarations have fallen under the label of Terrorism: 4 for the events of September 11th, 2 for the Oklahoma City bombing, and 1 for the 1993 World Trade Center explosion. This means the odds a federally declared disaster is a terrorist attack are 1 in 394.3.

The rarest of all: a tsunami. Just one—the wave that hit American Samoa last month—exists in FEMA’s records, making the odds a federally declared disaster is a tsunami 1 in 1,380.

For the inauguration of Barack Obama, the same rules were invoked in a new way. Because of huge crowds (six times the attendance of the inauguration before), President George W. Bush declared Washington, DC, a federal emergency area. The inauguration proceeded to go off without a hitch, making it the only federal emergency in history to be declared sans disaster.