Hennepin County Commissioner Mike Opat, who didn't seek re-election to an eighth term this year, will leave office Nov. 7, two months before the end of his term, he announced Tuesday.

Opat, 59, said he will begin a consulting practice, working initially with North Memorial Health's Robbinsdale campus in the First District, which Opat has represented for nearly three decades. The district includes Brooklyn Center, Brooklyn Park, Crystal, New Hope and Osseo.

The commissioner's departure will end a career with the county that began in 1981 walking the cellblocks of the workhouse as a corrections officer. Over time, he became a fixture in leadership with a deep understanding of the complexities of the sprawling public works and social services elements of the largest local unit of government in the state.

"Not for one day have I thought anything but that the county is a wonderful employer with truly dedicated employees," he said in his retirement notice. "I'm eternally grateful for the many talented leaders with whom I've had the chance to work over so many years."

Opat was elected in 1992, defeating John Derus partly by proposing 10-year term limits for commissioners. He stayed without significant opposition. Nine times his colleagues elected him County Board chairman.

He explained his plan for an early departure, just days after his successor will be elected, by saying he's "excited to move on to a new challenge."

The candidates seeking to replace Opat are Brooklyn Park Mayor Jeff Lunde and De'Vonna Pittman, disparity reduction coordinator for Hennepin County.

Opat is one of three incumbents who didn't seek re-election. Board Members Jan Callison and Jeff Johnson also are leaving.

A native of the North Side of Minneapolis, Opat came to office with a public policy degree from Harvard and a wonkish interest in politics but no political pedigree. He's been deeply involved in health and human services, roads and transit, but he will likely be remembered best as the architect of the public-private partnership to build Target Field, which opened in 2010.

"It has been an honor beyond description to work for and serve the residents of District 1 and all of Hennepin County," Opat said in a written statement.

Rochelle Olson • 612-673-1747

Twitter: @rochelleolson