This polygonal dataset shows the boundaries of the Spheres of Influence for cities in Napa County, California as of 2002. A sphere of influence is a planning boundary outside of a city's legal boundary that designates the city's probable future boundary. This file was created from LAFCO's hard-copy map tax rate area (TRA) database provided by the County of Napa Assessor. The hard-copy maps used to generate this layer are available from LAFCO. For more information on LAFCO of Napa County please see http://napa.lafco.ca.gov/