The Boston Atlas is a mapping application from the Boston Redevelopment Authority (BRA) that includes data from many Boston city agencies, plus information from neighboring towns and the state. Information such as the outlines of planning areas, building outlines, street edges, and property ownership can be turned on and off. And once a plug-in is installed, users can study their area of interest in 3-D.

The Boston Atlas application appears to be related to, or derived from, Bill Warner’s great site "Maps Over Time", although it’s not clear what the connection might be.  The BRA site also says "There is a new open source version of The Boston Atlas being tested. Please give it a try and report any bugs to greg@agog.com."  All this is a bit confusing, but the ability to view, draw, and compare maps for different parts of the city, with different layers turned on and off, is common to all these apps, and is a great educational tool.