This book assesses the 50 regional seismic networks funded by various federal, state, and private sources that operate autonomously in the United States. Most have aging equipment and suffer from declining sources of operating funds. Yet, they provide valuable scientific data as well as information about seismicity and earthquakes around their locales. The volume describes the advent of the new National Seismic Network, operated by the U.S. Geological Survey. The National Seismic Network provides a unique opportunity to integrate the regional networks with the national network. This system will preserve the valuable work of the regional networks and enhance the capabilities of the national network.