Elected a Tory member of the House of Assembly of United Canada in 1844, he was the leading figure in bringing about Confederation (1867) of the provinces of British North Canada as the Dominion of Canada after the passage of the British North America Act. He became the first Prime Minister (1867–73) of the new Dominion of Canada. During his years in office, which continued from 1878 to 1891, Canada expanded territorially and experienced growth in its economy, its internal communications, and its sense of national purpose.