Valley Forge, PA (Headquarters) Environmental Standard’s corporate office sits in the beautiful suburbs of Philadelphia, Pa, just a short drive from the city. Valley Forge, Pennsylvania boasts a historic national park, proximity to the King of Prussia Mall (the largest shopping mall on the East Coast), and handful of other great attractions and restaurants.  Address: 1140 Valley Forge Road PO Box 810 Valley Forge, PA 19482  Phone:610.935.5577