PORTLAND – Michael Chitwood resigned Monday after 17 years as the high-profile police chief of Maine’s largest city to head a department outside Philadelphia, the city where he grew up.

“I’ve had a great ride here,” said Chitwood, who is leaving to become police superintendent in Upper Darby, Pa., a densely populated township of 82,000. “This has been a difficult, gut-wrenching decision.”

Chitwood, 61, said family considerations led him to end the longest tenure as police chief in Portland’s history. He plans to leave Aug. 12 and begin his new job 10 days later.

City Manager Joe Gray, who joined Chitwood at City Hall to announce his resignation, said he plans to name an interim chief and conduct a national search for a successor.

Chitwood, whose familiarity with the news media made him a visible figure throughout the state, lavished praise on his 220-member department, the political leadership and the community at large.

“I will always consider Portland, Maine, to be my department,” he said.

Gray said Chitwood will be remembered for his efforts to promote community policing, crack down on domestic violence, and push for controls on handguns.

Recalling some of the changes he has seen during his tenure, Chitwood said the city has benefited from the rich cultural diversity arising from the arrival of immigrants from across the world. But he expressed concern about Portland’s problem of drug abuse and quality-of-life concerns linked to public drunkenness and people subjected to intimidation on the streets.

Chitwood said his new environment will represent “a total change.” Instead of looking out his window at Casco Bay, he said he will get to watch 50,000 cars passing by each day.

Chitwood, a former Philadelphia homicide detective, is perhaps best known for his work on the case against former counterculture guru Ira Einhorn, who was convicted in 2002 of murdering his girlfriend more than 25 years ago.