Most of the line currently used by route 70 was initially built and run by the Hawthorn Tramways Trust (HTT) in 1916–17. It ran between the Batman Avenue terminus (opposite Flinders Street station) to the intersection of Warrigal Road (then Boundary Road) and Riversdale Road. At the time, the HTT's Batman Avenue line was Melbourne's only electric tram line that reached the CBD. The Melbourne & Metropolitan Tramways Board took over the line in 1920, and in 1928, extended the line a further two kilometres to Wattle Park at the Riversdale Road and Elgar Road intersection.[1][2] In 1934, the line was given the route 70 designation, which it still holds today.[2][3]
On 6 June 1999 it was diverted to operate via the Exhibition Street extension with a four-lane divided road built over the Jolimont Yard, enabling Batman Avenue west of Melbourne Park to be closed with route 70 extended to terminate at the intersection of Flinders and Spencer Streets.[4][5] This new route was better able to serve all of the Melbourne Park venues such as the Melbourne Cricket Ground and Rod Laver Arena.[6] Extra sidings were also built along the route in order to accommodate special events.[7] On 5 December 1999, at the City end, the route was amended to terminate at new sidings west of Spencer Street.[8]
On 4 May 2003, the route was extended along Spencer Street to the intersection of Spencer and La Trobe Streets, swapping route termini with route 75.[9][10] Between May and November 2005, the route temporarily terminated at Market Street due to the closure and removal of the Flinders Street Overpass over King Street.[11] After the works were completed, on 21 November 2005, the route was re-extended along Flinders Street and its permanent terminus was altered to the intersection of Bourke Street and Harbour Esplanade at Docklands, no longer running along Spencer Street.[12] The route was extended to Waterfront City in September 2009 to replace route 48 which was re-routed away from Flinders Street and Waterfront City.[13][14]