During his tenure, Freeman added 24 fire stations and picked up firefighting for 8 cities.
He is credited with overseeing the development of specialized units, such as urban search and rescue and swift water response.
Freeman said, "I hate to leave. In many ways there's still much to be done and I guarantee you, I'll work till the last day I go out the door. But I will go out the door with a smile on my face. And thank you very much."
Freeman originally delayed retiring a year to help the department through budget cuts.
There has been no word about replacements.