The continuing rollout of phasor measurement units enables wide area monitoring and control (WAMS/WACS), but the difficulty of sharing data in a secure, scalable, cost-effective, low-latency manner limits exploitation of this new capability by bulk electric power grid operators. GridCloud is an open-source platform for real-time data acquisition and sharing across the jurisdictions that control a bulk interconnected grid. It leverages commercial cloud tools to reduce costs, employing cryptographic methods to protect sensitive data, and software-mediated redundancy to overcome failures. The system has been tested by ISO New England and the results reported here demonstrate a level of responsiveness, availability, and security easily adequate for regional WAMS/WACS, with the capacity for nation-wide scalability in the future.