The Courthouse Annex designed by ETB for the  Mercer County Commission was completed in July, 2005. The new facility houses the magistrate's offices, prosecuting attorney, family law master, and juvenile probation.

ETB was first asked to recommend the best location for the annex.  A major consideration was the ability to provide adequate parking. The site selected allows for easy access to the existing courthouse.The new annex also compliments the surrounding architecture of both the courthouse and the historic Memorial Building.