Gnowangerup is named as the place of the mallee fowl in the Aboriginal Noongar language, being derived from nearby Gnowangerup Creek and Spring, both names being first recorded in 1878. The name means "place where the mallee hen (Gnow) nests".
The town was first gazetted under the spelling of Ngowangerupp. Local dissatisfaction with this spelling led to it being altered to Gnowangerup in 1913.
The townsite was first gazetted in 1908.
Following a severe drought the town was flooded in 1940 after a torrential downpour. The bridge was covered by water, parts of the railway line, the local tennis courts and pavilion were washed away.
Gnowangerup State School was opened in November 1908 on a site on the northern edge of town. It is now known as Gnowangerup District High School and caters for students from Year 7 to 10.
The Memorial Hall was opened in 1923, the same year that electric light was being installed. The population of the town in the same year was 1,350 people.
A United Aborigines Mission, Gnowangerup Mission, was established on Muir Hill in 1935 on a 61 hectares (151 acres) site to replace the mission run on the Government reserve that ran from 1926 until 1935. The mission ceased operations in 1954 and then reopened as the Agricultural High School for Indigenous Australian boys.
In 1972 the Gnowangerup Noongar Centre was established by the New Era Aboriginal Fellowship operating out of a 1913 former bishop's residence that was also the headquarters of the Gnowangerup Noongar Corporation until 1989. The building was placed on the State Heritage Register. in 2012
The town also consists of a small industrial area where there are many different businesses, such as Auspan Group(sheds), Duraquip (transport engineers), Armadillo (lubricant supplies), BP Harris(engineers), Bulk spreading service, Topaz (roll tarps and seat covers), Browns Ag(spraying).
The Gnowangerup Star (1942–2003), also published as the Gnowangerup Star and Tambellup Ongerup Gazette (1915–1942), was a weekly English language newspaper published in Gnowangerup.
- Australian Bureau of Statistics (27 June 2017). "Gnowangerup (State Suburb)". 2016 Census QuickStats. Retrieved 20 September 2008.
- Western Australian Land Information Authority. "History of country town names – G". Retrieved 8 June 2007.
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- "Gnowangerup District High School". InHerit. Heritage Council of Western Australia. 27 November 1996. Retrieved 14 December 2017.
- "Farm & Station". Western Mail. Perth, Western Australia: National Library of Australia. 6 August 1910. p. 4. Retrieved 1 October 2013.
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- "CBH receival sites" (PDF). 2011. Archived from the original (PDF) on 18 March 2012. Retrieved 1 April 2013.