Career
He represented Grey North in the Canadian House of Commons from 1908 to 1917 as a Conservative and then from 1917 to 1921 as a Unionist Party member. He was born in Orangeville, Ontario, the son of John Middlebro, and was educated there and at Osgoode Hall. Middlebro was called to the Ontario bar in 1892.
He was mayor of Owen Sound from 1905 to 1909.
Middlebro was president and chairman of the board of directors for the Grey and Bruce Trust and Savings Company. He was named King"s Counsel in 1910.
Middlebro served as government whip from 1917 to 1921.