In the north Baja California and western Sonora region exists an important set of geologic faults, some of which extend southeast through the Gulf of California. These faults, which are part of the main border between the Pacific and North America tectonic plates, generate earthquakes of slightly over 7.0. An example of this is the 7.2 El Mayor–Cucapah earthquake of 4 April 2010. This and other past earthquakes caused severe damage and much concern among the inhabitants at both sides of the Mexico–US border. The Northwest Mexico Seismic Network (RESNOM) is a subnetwork of Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California (CICESE’s) network. RESNOM was designed to collect digital information from local and regional earthquakes that occur in the northern Baja California–western Sonora region. Although the design and installation of the network began in 1977, effective seismic monitoring began in June 1980. Through the years, RESNOM evolved from short‐period to broadband seismometers, accelerographs, and Global Positioning System (GPS) receivers collocated at each site. A description of this subnetwork and of some of the results obtained are presented here.