The State Plane Coordinate System (SPCS) is a map coordinate system commonly used in the United States. Most SPCS zones are based on the Transverse Mercator, Lambert Conformal Conic or Hotine Oblique Mercator projections. For more information, visit this site at http://en.wikipedia.org/wiki/State_Plane_Coordinate_System.
Simply click anywhere on the map and this mapplet will display the SPCS easting, northing coordinates. The datum transformation between the WGS84 datum used by Google Maps and the local NAD27 or NAD83 projection datum is done using the Standard Molodensky transformation. Parameters for the datums and ellipsoids are taken from the University of Colorado.