Considered as one of the most significant developments of smart grid technology, wide area monitoring system (WAMS) utilizing synchrophasor measurements has been expected to help create a more reliable and efficient electric power infrastructure. The use of phasor measurement units (PMUs) can help with understanding, predicting, or even controlling the status of power grid stability in real time. A power system frequency monitoring network (FNET/GridEye) was first proposed in 2001 and then established in 2004. As a pioneering WAMS, it serves the entire North American power grid and other main power grids worldwide through advanced real‐time situational awareness techniques, such as real‐time measurement visualization, accurate disturbance location estimation, and interarea oscillation modal analysis. Furthermore, taking advantage of the vast historical database, postevent analysis, measurement‐aided model validation, and other nonreal‐time applications have also been investigated. Dozens of papers published in the past 10 years had discussed the FNET/GridEye's various functionalities. This chapter summarizes the FNET/GridEye work and presents some of the latest implementations of FNET/GridEye's applications.