This presentation will summarize work on the Pacific Northwest Smart Grid Demonstration Project. A key element of the project is development and implementation of a technique referred to as transactive control. Transactive control will provide a means of coordinating the response of smart grid assets at all levels of the power system. In simple terms transactive control may be thought of as extending the notion of locational marginal pricing throughout the power system from generation to end-use. The transactional nature of the technique, however, introduces a new element in the use of a pair of signals to implement an equivalent to market closing distributed in space and time.