Supervisory control and data acquisition (SCADA) systems are widely used in the critical infrastructure. These systems are high risk targets for cyber attacks due to their criticality, interconnectedness and Internet accessibility. SCADA systems employ programmable logic controllers to monitor and issue control instructions to other devices. Unfortunately, programmable logic controllers are typically configured in a persistent manner – they are configured once and designed to operate continuously. They are, therefore, ill-suited to operate in virtual, dynamic and cyber-resilient environments. SCADA systems must employ cyber-resilient architectures to enable them to endure and recover from cyber attacks.This chapter describes a secure methodology for storing SCADA system states that can be used by redundant, non-persistent devices during operations and recovery. The proposed methodology realizes a non-persistent, Byzantine fault-tolerant, virtual industrial control system architecture whose state and function can be stored and restored securely, contributing to its cyber resilience. Implementation of the methodology in a SCADA environment incorporating non-persistent programmable logic controllers reveals that cyber attacks are identified quickly and secure restoration can occur without loss of state or functionality. Mathematical and timing analyses demonstrate the applicability and efficacy of the methodology in creating cyber-resilient SCADA systems.