Missouri State Highway Patrol Capt. Ron Johnson, left, speaks to protesters as he walks through a peaceful demonstration as communities continue to react to the shooting of Michael Brown in Ferguson, Mo., on Aug. 14.  (Lucas Jackson/Reuters)

After days of protests and police responses in the St. Louis suburb of Ferguson, Missouri Gov. Jay Nixon (D) responded Saturday by declaring a local state of emergency. A curfew was set but has since been lifted, although neither development seems likely to dampen the protests or the swell of interest in the shooting that set the nation on edge.

Some fear the state of emergency could backfire — as they often have for previous states of emergency prompted by unrest.

States of emergency on the state and local level happen all the time, but it's important to note how rarely politics are the immediate instigator for declaring them. For many local officials, nature and disease are the more likely causes of such a declaration.

Declaring emergencies after hurricanes, tornadoes and forest fires has become familiar, especially as the pace of  inclement weather seems to increase indefinitely. Before Hurricane Sandy, New Jersey Gov. Chris Christie (R) declared a statewide state of emergency. The forest fires in California this summer prompted Gov. Jerry Brown (D) to declare a state of emergency. After basically every large snowstorm or drought, you see the same. States of emergency of this type are so commonplace as to run together in a entirely unremarkable way, at least on the national level.

Other states of emergency trend toward the more unexpected. Days before Nixon declared a local state of emergency in Ferguson, New Hampshire Gov. Maggie Hassan (D) declared one in her state after 41 people in Manchester overdosed on "Smacked!" a synthetic marijuana known as "spice" that is typically found at gas stations and meant to be used as incense. Declaring a state of emergency means that New Hampshire can quarantine certain brands of spice.

Drug overdoses often prompt emergency declarations. In March, Massachusetts Gov. Deval Patrick (D) declared a state of emergency in an effort to combat heroin overdoses. First responders were ordered to carry a drug that can reverse the opiate's effects immediately.

Fears of contagious illnesses can also prompt emergency declarations. In 2007, California Gov. Arnold Schwarzenegger (R) declared one because of fears concerning the spread of West Nile virus.

Then there are the states of emergency with obvious political underpinnings, whether caused by physical or fiscal discontent. These states of emergency — unsurprisingly, given their overt brush with politics — also face the most pushback. After last year's government shutdown, nine counties in Utah declared a state of emergency, claiming "economic disruption." In Western states, dominated by federal land and national parks, tourism revenue from federally funded parks is essential. So the counties wanted the state to do something about it, shutdown be damned. In Maine, Gov. Paul LePage (R) also declared a state of emergency due to the shutdown, so he could rearrange state operations while employees were being laid-off. Unions called the move a "power grab."

In 1979, Missouri Gov. Joseph Teasdale (D) declared a state of emergency during a firefighter strike in Kansas City. The National Guard began covering for the federal employees, who had been calling in sick by the hundreds.

And then there is Ferguson, and the similar states of emergency declared before it. Much of the dismay over Nixon's declaration could stem from the fact that similar states of emergency were declared during previous protests with racial underpinnings. In 1971, a black farm worker was killed by a white state trooper in Ayden, N.C. More than 800 protesters were arrested in the following days, charged with gathering en masse during a state of emergency. In 1972, Louisiana Gov. Edwin Edwards (D) declared a state of emergency after two black students were killed during protests at Southern University. The National Guard was called in, and journalists were barred from speaking with students. Dorm telephones were shut off. The shooters were never identified.

After Rodney King was beaten by police officers in 1991, Los Angeles mayor Tom Bradley declared a state of emergency in response to the riots. The governor of California sent in the National Guard. In 2001, the mayor of Cincinnati, Ohio, declared a state of emergency and curfew after a 19-year-old unarmed black man was killed by a white police officer. Tear gas and rubber bullets were used against protesters.

Despite the many different immediate reasons for declaring a state of emergency, they are often only necessary because the communities involved had preexisting problems that had been ignored or put off. If a state's infrastructure bends to the will of the weather, there is no option but to expend massive resources to fix things up after disaster. If the state coffers aren't prepared for financial calamity, a back-up plan that perhaps fudges the rules might seem prudent. If federal employees aren't kept happy, services may fall by the wayside.

And if long-standing racial issues are left unaddressed, unrest will often erupt. These realities have prompted states of emergency for decades. Whether the short-term measure will lead to any big picture change-ups remains to be seen.