Jackson was born in 1832 in Providence Green, Green Hammerton, near Harrogate, Yorkshire, England. He was the son of Samuel Jackson, a brewer and yeoman who owned and farmed his land, and Sarah Jackson, the daughter of a Welsh revenue collector. His mother died when he was four. He had three brothers and a sister; all but one of the brothers emigrated to New Zealand. His parents had married on 24 March 1828. His oldest sibling was his sister Ann. She died three days after giving birth to her first child. His eldest brother was Samuel, who studied law, was called to the bar in 1853, and emigrated to Auckland in 1856, where he became a prominent lawyer. William himself was the third of the children; he was born on 11 October 1832 and baptised a month later on 12 November. Thomas was the next sibling. He became a mariner and also emigrated to New Zealand. His youngest brother, John, remained in England and became a prominent neurologist. He emigrated to Australia in 1857 to join the Victorian gold rush. Sometime later, he went to New Zealand to join two brothers who were already there. His wife was Bridget.
New Zealand
In New Zealand, Jackson first farmed in Mangatawhiri, then Rangiaohia, Kihikihi, and then Papakura. When the Invasion of Waikato commenced, Jackson organised a local militia that became known as Jackson's Forest Rangers, and he was commissioned as Major Jackson. When militia stole a Māori flag, his wife hid it under her dress, wearing it as a petticoat. In retaliation, Jackson's house was burned down twice. He represented the Waikato electorate from to 1875, when he retired. He then represented the electorate from to 1889, when he died. As a politician, it is said that he was as vigorous as he had been as a militia leader. During his times in parliament, he supported the Stafford and Atkinson Ministries. Jackson went missing during a voyage on the SS Rotoruaen route from New Plymouth to Onehunga. He disappeared during the night of 29/30 September 1889, and it is assumed that he got sick, went on deck and fell over board. The Jacksons had no children.
