Bureau of Justice Statistics: Local Police
"More than 12,000 local police departments were operating in the United States during 2016. A local police department is a general-purpose law enforcement agency, other than a sheriffs' office, that is operated by a unit of local government, such as a town, city, township, or county. Tribal police are classified as local police in Bureau of Justice Statistics data collections." -- From Website.
May include some Michigan data.