Steward was born in Reading, Berkshire, in England, and emigrated to New Zealand in 1862, settling in Canterbury. He worked as a journalist for the North Otago Times in Oamaru.
In 1871 he was elected as Member of the House of Representatives for Waitaki. He was defeated in the 1875 election, but was re-elected in 1881. He held his seat, through several boundary changes, until 1911, when he was appointed to the Legislative Council.
Steward was elected Speaker when the First Liberal Government came to power in 1891, and held the position until 1893. He was knighted in 1902.