A divinity student, he joined John Gooch Robberds, the minister of the Unitarian Chapel in Manchester, in August 1828. Gaskell met Elizabeth Stevenson, the daughter of John Stevenson, a former Unitarian minister. The couple had similar ideas on religion and social reform and were married on 30th August, 1832.
Most of William Gaskell's parishioners were textile workers and Elizabeth was deeply shocked by the poverty she witnessed in Manchester. Later, Elizabeth wrote a novel, Mary Barton: A Tale of Manchester Life that attempted to illustrate the problems faced by people living in industrial towns and cities. As a result of this book and other novels such as Cranford and North and South, Elizabeth Gaskell became one of Britain's most popular novelists.
William Gaskell had a tremendous influence on the people of Manchester. An outstanding lecturer, he was appointed professor of English history and literature at Manchester New College in 1846. He was also responsible for establishing evening classes at Owens College and from 1858 taught at the Working Man's College in Manchester. From 1861 to 1875 Gaskell was also editor of the Unitarian Herald.
Gaskell was a preacher for the British and Foreign Unitarian Association and in 1876 became principal of the Unitarian Missionary Board. Gaskell also wrote several pamphlets and hymns. William Gaskell died in Manchester on 11th June, 1884.