The third section of the line, Kukerin to Lake Grace, 40 kilometres (25 mi), was awarded to the PWD on 19 July 1915 and opened 18 June 1916.

[3] The official opening took place in the presence of the Premier of Western Australia, John Scaddan, and the Minister for Works, William Angwin.

[8] The final 63-kilometre (39 mi) 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.

[9] On 2 June 1930, the contract for the branch line from Lake Grace to Hyden was awarded to the Public Works Department.

[3] In 1954, the state government of Western Australia had compiled a list of loss-making railway operations, of which the Lake Grace to Newdegate and the Lake Grace to Hyden lines were part, having had a total expenditure of almost four times their earnings in the financial year to June 1953.

[10] 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.

[26] The heritage listed Wagin Railway Station was completed on 25 April 1911, replacing an early building that was relocated in 1906.

[30] On the Hyden branch line, the Pingaring Railway siding precinct is on the Shire of Kulin's heritage list.