The number of inmates in state prisons across the country declined by more than 29,000 last year, with Minnesota's incarceration rate among the nation's lowest, according to federal statistics released Thursday.

In 2012, 1.57 million people were estimated to be in state and federal prisons, a decline of 1.7 percent (or 27,770 inmates) from 2011, according to the Justice Department's Bureau of Justice Statistics.

This is the nation's third consecutive year of decline in the number of state prisoners, which represents a shift in the direction of incarceration practice in the states over the past 30 years, the bureau said.

The U.S. prison population peaked at 1.61 million in 2009.

Maine had the lowest imprisonment rate among states (145 per 100,000 residents), followed by Minnesota (184 per 100,000) and Rhode Island (190 per 100,000), the bureau said.

The rate per 100,000 in Minnesota has fluctuated since early last decade, ranging from a low of 141 per 100,000 in 2002 to 189 per 100,000 in 2009, according to data from the state Department of Corrections (DOC).

In numerical terms, Minnesota's prison population has remained fairly steady over the past several years, holding in the 9,000 to 9,650 range since 2006, according to the state data. As of Jan. 1, the total stood at 9,452.

According to the bureau, in 2012, states with the highest imprisonment rates were Louisiana (893 per 100,000), Mississippi (717 per 100,000), Alabama (650 per 100,000), Oklahoma (648 per 100,000) and Texas (601 per 100,000).

The decline in the state prison population contrasts with an increase in the number of federal inmates. The federal prison population grew by 0.7 percent (or 1,453 inmates) during 2012, a slower rate than the average annual increase of 3.2 percent over the past 10 years.