The Great Southern Railway, passing through Wagin, was established in 1889, having been constructed in a three-year period from 1886. The '
, an act by the Parliament of Western Australia granted assent on 23 December 1905, authorised the construction of the railway line from Wagin to Dumbleyung. A second act, the ', was assented to 16 February 1911, authorising the construction of the extension to Kukerin. The third act, the '''', was assented to on 12 January 1915, approving the construction of the line from Kukerin to Lake Grace. The Wagin to Newdegate railway line's contract for construction for the first section from Wagin to
Dumbleyung, , was awarded on 3 June 1906. It was constructed by the Western Australian
Public Works Department (PWD) and opened on 19 February 1907. The second section, from Dumbeleyung to
Kukerin, , was awarded on 17 May 1911 and opened on 3 May 1912, again constructed by the PWD. The third section of the line, Kukerin to Lake Grace, , was awarded to the PWD on 19 July 1915 and opened 18 June 1916. The '''' was assented to on 22 December 1923, approving the construction of the line from Lake Grace to Newdegate. The final section of the railway line from Lake Grace to Newdegate was awarded to the PWD on 16 January 1925 and opened on 15 February 1926. On 2 June 1930, the contract for the
branch line from Lake Grace to Hyden was awarded to the Public Works Department. The line, long, was opened on 5 April 1933. In December 2000, Westrail's freight operations and a 49-year lease of Westrail's freight network, including the Wagin to Newdegate railway line, was sold to
Australian Railroad Group (ARG), a joint venture between
Wesfarmers and
Genesee & Wyoming. ARG set up a subsidiary,
WestNet Rail, to manage the below-rail operations. In February 2006, it was announced that ARG would sell WestNet Rail to
Babcock & Brown, and the above-rail operations would be sold to
Queensland Rail. Babcock & Brown Infrastructure was renamed Prime Infrastructure in October 2009, and in 2010, the company merged with
Brookfield Infrastructure Partners. In August 2011, WestNet Rail was rebranded Brookfield Rail, and in July 2017, Brookfield Rail was rebranded as Arc Infrastructure. In 2010,
CBH Group, the grain growers' co-operative, signed a 10-year contract with
Watco Australia to operate CBH trains. The contract commenced at the start of May 2012, upon the ending of CBH's contract with ARG. The contract with Watco ended six months early, with a new six-year contract between CBH and
Aurizon commencing in late 2021. Arc Infrastructure deems the railway line to be part of its Grain Freight Rail Network, which, in 2017, accounted for 50 percent of its network but only 10 percent of its freight. The entire line to Hyden and Newdegate was classified as
Tier 1. ==Elevation==