The City of Lowell's GIS maintains a large amount of data in "layers" which can be overlaid onto City maps.
These layers include building footprint locations, address information, the street centerline network, railroads, waterway and wetlands areas, paved roadways, schools, neighborhood boundaries, election wards and districts, zoning boundaries, police and fire stations, and a digital parcel base map that displays the information taken from the hard copy Tax Assessor maps. The maps are rendered through ESRI's ArcGIS suite of tools, and presented using Applied Geographics' General Purpose Viewer (GPV).
Note that use of the City's GIS data, layers, and maps, requires acceptance of the City's Disclaimers and Terms of Use.