Description: Incorporated city and town limits in Yellowstone County The boundaries are generally based on parcel data which is based on the USDI Bureau of Land Management's (BLM) Geographic Coordinate Database (GCDB). The GCDB is a complex measurement management system that uses a least squares adjustment of existing survey data to come up with a digital representation of the Public Land Survey System (PLSS). For more information on GCDB, see the Montana/North Dakota BLM website at http://www.mt.blm.gov/cadastral/gcdb/index.html. Accuracy varies between townships and it is important to note that the accuracy of the data can't be any more accurate than the GCDB.