WSR-74s were added to the radar grid in 1974 and were used in conjunction with the older “57s,” as they were called. It was not until 1988, however, that the Next Generation Radar (NEXRAD; also called WSR-88D) were built using the newer Doppler technology. The first NEXRAD was deployed in Norman, Oklahoma, in 1990. There are now 160 NEXRAD radar stations throughout the United States.