The Armadale line opened on 2 May 1889. An 1891 contract tender described the route of the new line from East Perth to Pinjarra: The original stations in 1889 were Perth, Welshpool, Kelmscott and Armadale. Cannington, although operational in 1889, was opened in 1893. The following stations were opened:
Victoria Park in 1898, rebuilt 230 metres south in 2008
Woodlupine in 1899
Goodwood in 1906
Burswood, in 1906
Mint Street in 1912
Seaforth on 4 May 1948
Higham in 1954
Oats Street in 1954
Stokely in 1954, closed 15 April 1989.
Tredale, opened in 1956 as Armadale School siding, renamed Tredale in 1959, closed in 1989.
In September 1991, the line commenced electrified operation. Between 2004 and 2005, Armadale, Carlisle and Gosnells were upgraded to provide better facilities to passengers and provide better access between trains and buses. Lathlainstation was closed on 3 February 2003 as part of the project. Thornlie was opened on 7 August 2005. The station is built on a spur line of the Armadale Line. Between 21 March 1993 and 8 August 2005, trains on the Armadale line continued through Perth to the Joondalup line. In 2004 new railcars were introduced, which became exclusive to the Joondalup line. From 2005 until 2012, Armadale Line trains did not run through Perth to the other lines but on 20 August 2012, as part of works relating to the Perth City Link project to sink the Fremantle line, services from Fremantle connected to the line until the tunnel was opened on 18 July 2013 which saw the Armadale Line terminate in Perth again. Victoria Park and Kelmscott Stations were upgraded between 2007 and 2008 as part of the Public Transport Authority's 'Building Better Stations' program. Victoria Park station was opened on 20 July 2008. and Kelmscott was opened on 21 November 2008. As part of the new Perth Stadium project, Belmont Park station closed on 13 October 2013. Perth Stadium station was opened in 2018 to replace it.
Below is the annual patronage of Armadale and Thornlie railway lines from 2010–2011 financial year. Figures are provided as total boardings, which includes all fare-paying boardings and free travel on stations within the free transit zones as well as transfers between stations. The figures for rail replacement and special events services are not included in the total.
Railway stations
During peak hour times on weekdays, some railway stations are almost always bypassed to enable faster commutes. Express trains also run along the Armadale line on weekdays, and even often on weekends.