The concept behind declaring a state of emergency is to allow the government the ability to change certain functions of their legal, legislative or executive operation during that time. In the United States, there can be a national state of emergency or a local state of emergency. The local declarations are generally done by governors in response to natural disasters, while national declarations are more related to international events and conflicts.
There have been a number of long running emergency states in America over the years. In 1933, the banking crisis triggered a state of emergency as did the 1950's Korean War. Two declarations issued in the early 1970's relating to the postal strike and the rampant inflation all remained in force for some time.
However, none have exceeded the 35-year duration of the state of emergency declared in 1979 by President Jimmy Carter in terms of the Iran Hostage Crisis. This state has been extended by all subsequent presidents, most recently having been extended in November 2013 by President Obama owing to the increased tensions between the US and Iran.
