The National Weather Service Chicago, headquartered in Romeoville, Illinois, monitors weather for 23 counties across Northern Illinois, the Chicago metropolitan area, and Northwest Indiana. Its history dates back to October 15, 1870, when the Army Signal Service established the region's first federal weather office in Chicago, later expanding its forecast area to the Rocky Mountains in May 1894. Over the years, the office relocated from the University of Chicago to West Pershing Rd in the early 1970s, and its transmitter was moved to the Sears Tower (now Willis Tower) in 1975. As one of only two NWS offices in Illinois, it now operates 11 NOAA Weather Radio stations (including KWO39 and KZZ81) that serve marine, aviation, and public safety needs. Notably, the radio service began in 1954 for aviation, was revived for marine use in 1958 following meteorologist Ivan Brunk's suggestion, and later expanded to public forecasts, making it a vital resource for the region's millions of residents.