William Henry Carpenter was born in Stratton, Wiltshire in the United Kingdom on 5 April 1863, son of a carpenter/boilermaker. He was educated in Swindon and was an apprentice on the Great Western Railway before migrating to Victoria in 1886 where he was employed in Ballarat as a boilermaker on locomotive construction.

In 1889 in Albert Park he married Alice Ross and two years later moved to South Australia where he was employed as a working foreman in Gawler for five years before securing election as a Labor candidate to the South Australian House of Assembly in 1896 as the second of two members for Encounter Bay: the first elected was future federal Labor politician King O'Malley, who at that time stood as an Independent Liberal. O'Malley was defeated in 1899 when Carpenter was re-elected but he in turn lost his seat in 1902 when he finished fifth in a contest for four places representing the redrawn constituency, Alexandra.

In the following year Carpenter moved to Western Australia and was employed in railway workshops in Fremantle becoming president of the Australian Labor Federation Fremantle District Council and the Transcontinental Railway League. At the second federal election in December 1903 Carpenter defeated Solomon for the Fremantle seat, polling more than 61 per cent of the vote in a two cornered contest. However, in 1906 he lost the seat to Western Australian Party candidate William Hedges by a little over 100 votes and in 1910 by almost 1300 votes when Hedges stood as a Liberal candidate. Carpenter also failed to win election as the ALP candidate for the West Province in the Western Australian Legislative Council in 1908.

After his defeat in 1906 Carpenter had worked in a secretarial and agency business and as a journalist until his return to parliamentary politics in October 1911 when he won the Western Australian Legislative Assembly seat of Fremantle defeating the sitting non-Labor member. He retained the seat in the 1914 election but in 1917 parted company with the Labor Party over the conscription issue. Standing as a National Labor candidate he lost the seat in the general election to the endorsed Labor candidate.

An active church and temperance worker Carpenter moved to Melbourne and then to Sydney. On 11 September 1930 his body was found floating in a river in the Hacking River National Park in Sutherland, New South Wales.