[7] It also allowed services to begin from Liverpool or Lidcombe and reach the City Circle via Bankstown and Sydenham without using the Main Suburban railway line.

[14] Railway authorities initially conceived of the line as a opportunity to alleviate pressure on the Old Main South railway line by providing an alternate route to Liverpool, and also to advance development of the intervening land.

[15] Increased suburban development prompted the line to be extended to Bankstown on 14 April 1909, with intermediate stations at Lakemba and Punchbowl.

[6] This allowed trains to operate to Liverpool, or in a loop back toward the City Circle via Lidcombe and the Main Suburban railway line.

To service the new electric rolling stock, Punchbowl Maintenance Depot was built on the line just east of Bankstown.

[20] This will allow much a higher frequency service and will alleviate bottlenecks in the Sydney Trains system, but ensuring the line meets modern metro standards is a technically challenging undertaking, particularly with some of the stations which have curved platforms over a century old.

[22] Intermittent temporary closures began in December 2019 for works to prepare for the conversion to metro standards, with the expectation of a longer, extended closure to occur immediately prior to the commencement of metro services.

[23][24] In 2023, with conversion of the line having fallen a year behind schedule,[25] the NSW Government announced that the opening of Sydney Metro City & Southwest would be staged, with metro services not reaching Bankstown until late 2025, after a 12-month closure of the line for conversion works.