The Eastern Suburbs & Illawarra railway line is a commuter railway line in the eastern and southern suburbs of Sydney, that has become part of the city's CityRail rail network. Along with the South Coast Line, an intercity line that uses the Illawara Line tracks out of Sydney, the line was originally constructed in the 1880s to Wollongong to take advantage of agricultural and mining potentials in the Illawarra area. In 1926, it became the first railway in New South Wales to run electric train services. Today the railway consists of three connected lines: the original Illawarra Line; a branch line between Sutherland and Cronulla (the Cronulla Line), which opened on a former tramway alignment in 1939; and an underground rail link between the Sydney CBD and Bondi Junction, the Eastern Suburbs Line, which opened in 1979. The railway currently operates as a relatively high-frequency independent line today, that has been noted by the New South Wales Government to be the most reliable line in Sydney. Operationally and historically, the entire line from the Illawarra Junction at Redfern to its terminus in Bomaderry on the South Coast was known as the "Illawarra Line", however, since 1989, CityRail has marketed the suburban services to Waterfall and Cronulla as the "Illawarra line" and interurban services south to Wollongong and Bomaderry as the South Coast Line. The line is coloured an azure blue on CityRail's timetables and other promotional materials.