Martial law in the United States refers to times in 
United States history in which a region, state, city, or the whole 
United States was placed under the control of a military body. On a national level, both the 
US President and the 
US Congress have the power, within certain constraints, to impose 
martial law since both can be in charge of the militia. In nearly every state, the governor has the power to impose martial law within the borders of the state. In the United States, martial law has been used in a limited number of circumstances, such as New Orleans during the 
Battle of New Orleans; after major disasters, such as the 
Great Chicago Fire of 1871, the 
1906 San Francisco earthquake, or during riots, such as the 
Omaha race riot of 1919 or the 
1920 Lexington riots; local leaders declared martial law to protect themselves from mob violence, such as 
Nauvoo, Illinois, during the 
Illinois Mormon War, or 
Utah during the 
Utah War; or in response to chaos associated with protests and rioting, such as the 
1934 West Coast waterfront strike, in Hawaii after 
Japan's attack on Pearl Harbor, and during the 
Civil Rights Movement in response to the 
Cambridge riot of 1963