Born in Nelson Township, Halton County, Canada West, Henderson was educated at the Milton Grammar School and the Normal School of Toronto, and initially worked as a teacher in Nelson, later becoming a deputy registrar for the County.

[5] He later settled in Acton, Ontario, and operated a general store in partnership with David Darling Christie, his brother-in-law.

[10] He was first elected to the House of Commons of Canada for the electoral district of Halton in an 1888 by-election after the sitting MP, John Waldie, was unseated for bribery by agents.

His election was seen as being significant, in that he won through the support of the rural parts of the riding while voters in Milton and Georgetown swung more towards the Opposition candidate.

In recognition of his long service in the House of Commons, he was made a member of the King's Privy Council for Canada in February 1916.