UPDATE: 2011.09.03
MyLocalCrime.com (associated with SpotCrime.com) is another free web site that maps Prince George's County crime incidents, currently going back to at least December 2010. In MyLocalCrime.com you can only set the location; you can not change the incident types or time-frames to be displayed. There is a date sorted list of incidents at the bottom of the page. MyLocalCrime.com has only 8 incident types: Arrest, Arson, Assault, Burglary, Robbery, Shooting, Theft, Vandalism, plus "Other". CrimeReports.com has more crime types and Fire and EMS, traffic enforcement, quality of life incidents, etc. Sometimes MyLocalCrime.com has incidents a day earlier than CrimeReports.com. CrimeReports.com uses distinctive map icons for "theft of vehicle", "theft from vehicle", and "other thefts". MyLocalCrime.com and SpotCrime.com have only one map icon for all kinds of "theft" -- you must click on the icon to learn what type of theft it was.
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CrimeReports.com is where Prince George's County Police Department (and other police departments in Maryland and across the country) now publicly release crime incident data for free, based on calls for police response to the Prince George's County Public Safety Communications Center (Police, Fire, and EMS Emergency 911 and the new non-emergency 301-352-1200 ). There you will find past incidents up to six months back. To see incidents in your local area, enter your ZipCode in the Search field (or you could use a local address to center the map on). Be sure to set the date range and the incident types that you want to be displayed. Also look for the pop-out list of date-sorted incidents at the left edge of the screen. You can set up daily, weekly or monthly email alerts based on your chosen search criteria.