A National Online Parcel-Level Map Data Portal (NPDP) is provided that optimizes online delivery of parcel-level maps and linked attribute data. To do this, the NPDP manages a database of assembled and current vector based parcel data in a spatial format (GIS) that enables geocoded parcel boundaries to be linked to property tax records. A user enters a street address into an appropriate screen window to call up and view road right-of-ways, all parcel boundaries and the "exact" address location as a highlighted parcel area. In addition, a list of property record attributes such as owner, use code, assessed value and year constructed can be displayed. Other on screen parcels can likewise be selected if one wishes to view their linked attributes. Subscribers may customize the NPDP to perform a variety of spatial analysis/reporting functions. Under public/private alliances, agreements are negotiated with individual property assessor's offices whereby they receive a portion of NPDP service provider revenue in return for parcel map database updates. Such on-going commerce between data sponsors and the NPDP service provider is utilized to assure a sustained and expanding flow of increasingly competent content.