Local Police Departments

Annual report. Boston (Mass). Police Department. 1st- ; 1906- . FindIt@Harvard

Annual report of the Board of Police for the City of Boston, 1884-1906. FindIt@Harvard

Boston Police Department Reports (1885-2005)

Boston Police Strike of 1919

Policing the city : Boston, 1822-1885, by Roger Lane. Cambridge : Harvard University Press, 1967, 299 p.
HOLLIS Records
--APPENDIX I. A Note on Criminal Statistics (p. 225-229
--Notes on Sources (p. 239-248)

Annual report of the Police Department of the City of New York, Statistical Reports, complaints and arrests, and other sources available at the John Jay College of Criminal Justice

In Hathitrust catalog search you can search keywords: police report, and Limit To: Full view only.  On the left side of the Results page, you can limit to Place of Publication: United States.  Be careful with date limitations.  If you want a report for 1950, the report series may have started in, say, 1923, and 1923 will be the date on the HathiTrust record.

Publications of many police departments can be found in HOLLIS or WorldCat by searching in HOLLIS on Police Periodicals as a Subject keyword search and adding the name of your city/state of interest.

Often local public or university libraries will have research guides for city documents.  Go to local library websites and look for Research Guides or Google, for example: Chicago library guide crime or police

Examples:
New York City Documents
Baltimore
Chicago Research Guide: Primary Sources/Stats
Chicago Government Information: Crime & Police

The Digital Public Library of America offers textual, visual, and sound resources contributed by numerous libraries, archives, and museums.  Searches catalog records, not full text, and links to the items on the contributors' websites.  Contains many individual items, such as letters and photographs, from digital collections.

Umbra Search is a search engine for African American digitized materials in numerous repositories

Digital Libraries by State

These websites list hundreds of local, state, and regional resources. Each is different and some are better designed than others.  Very useful when your topic has a regional focus.