surface streets. As it exits Rockford, Route 251 serves as the primary north-south thoroughfare of its northern suburbs, from Loves Park to South Beloit. During the late 1970s and early 1980s, US 51 was replaced by the construction of Interstate 39. Directly connecting Rockford to Bloomington-Normal, I-39 has a northern terminus at the US 20 bypass and is connected to I-90, using the latter route to access I-90. The north-south four-lane interstate gives access to Peoria and the Quad Cities; with access to Interstate 80 and Interstate 88, Interstate 39 allows for Rockford access to the southern suburbs of Chicago, also serving as a bypass around Chicago to Wisconsin. Other roads/highways Illinois Route 2 (South/North Main Street) Illinois Route 70 (Kilburn Avenue) Illinois Route 251 (North Second Street, Kishwaukee Street, Harrison Avenue, 11th Street) Raoul Wallenberg Expressway (proposed, never built) Bus The Rockford Mass Transit District (RMTD) provides fixed-route and paratransit service, with a service area including Rockford, Loves Park, and Machesney Park. The 40 fixed route buses operate over 17 routes Monday thru Saturday, 6 night routes and 5 routes on Sundays. Current intercity bus providers in Rockford are Greyhound Lines and Van Galder Bus Company. Bicycle-sharing system In April 2018, Rockford became included in the LimeBike bicycle-sharing network. Using 500 commuter bicycles supplied by the company, residents rent bicycles through a mobile app, unlocking the dockless bicycles. Distinguished by their bright green color, LimeBikes are equipped with a basket, lights, and GPS (to locate them for rental); one-speed and three-speed units are in use. In early 2019, LimeBike was discontinued in Rockford; the company shifted its business model away from bicycles to e-scooters. Air The first airport serving the Rockford area was Machesney Airport, located north of the city alongside US 51. Opened in 1927, the airport was initially a private airport; during World War II, it was utilized by the Army Air Corps. After the war, Machesney Airport was opened as a municipal airport. In 1974, the location was closed, becoming the site of the Machesney Park Mall in 1980. Following the final closure of Camp Grant in 1946, the state legislature allowed for the establishment of an airport to serve Rockford, leading to the creation of the Greater Rockford Airport Authority (GRAA). In 1948, the GRAA received a 1500-acre portion of the Camp Grant property between US 51 and the Rock River, located between the southern