The United States Peace Index, produced by Institute for Economics and Peace, found Cambridge, Mass., the most peaceful metropolitan area and Detroit the most violent.
The index analyzes peacefulness at the state and city levels, via five indicators: The number of homicides, number of violent crimes, the incarceration rate, number of police employees and the availability of small arms.
There were improvements in all indicators from the 2011 to the 2012 Index. The national homicide rate decreased by 3.78 percent, the violent crime rate fell 6.03 percent and the total number of state prisoners fell by 0.6 percent.
Following Maine as the most peaceful states were: Vermont, New Hampshire, Minnesota, Utah, North Dakota, Washington, Hawaii, Rhode Island and Iowa. Following Louisiana as the most violent states were: Tennessee, Nevada, Florida, Arizona, Missouri, Texas, Arkansas, South Carolina and Alabama.
Vermont, New Hampshire and Iowa tied for the least number of homicides with Louisiana the most -- four times as many homicides.
Maine had the lowest violent crime rate and Nevada had the highest. Maine also had the least amount of residents incarcerated, with Louisiana the highest -- almost five times the rate of Maine, the index said.
New Jersey had the highest level of police officers, with Maine the lowest.
Rhode Island, Massachusetts and Hawaii had the lowest levels of handguns, with Mississippi the highest.