The King County web mapping application “Census Viewer” has been retired. Census information for King County and the Puget Sound region can be found at the following U.S. Census Bureau links.
Many Census datasets in GIS formats (for use with GIS software and GIS mapping applications) can be downloaded from the King County GIS Data Portal. Click through to the download page by accepting the terms and conditions and then look for the data layers in the "Census" category. The GIS data layers can be downloaded as an entire set, which includes the Census layers, by category (so just the Census layers, if that is all you want), and by individual feature layer.
King County GIS Center staff are available to help you navigate the various Census datasets that are available in the KCGIS Data Portal and in the internal KCGIS Data Warehouse. Please contact Mary Ullrich (206-684-1789) or Cheryl Wilder (206-263-5220) for more information.