Process Control System (PCS) security is critical to our national security. Yet, there are a number of technological, economic, and educational impediments to PCS owners implementing effective security on their systems. OPSAID (Open PCS Security Architecture for Interoperable Design), a project sponsored by the US Department of Energy’s Office of Electricity Delivery and Reliability, aims to address this issue through developing and testing an open source architecture for PCS security. Sandia National Laboratories, along with a team of PCS vendors and owners, have developed and tested this PCS security architecture. This report describes their progress to date.