He was born in Saint-Hermas, Quebec in 1875, the son of Isidore Proulx, and grew up in Plantagenet, Ontario. Proulx studied at the Collège Bourget in Rigaud, Quebec, the University of Ottawa, Saint Michael's College in Toronto and Osgoode Hall. He articled in Ottawa and Toronto, was called to the bar and set up practice in L'Orignal in 1904. He was elected to the House of Commons later that year in a by-election held after the death of his father. In 1907, he married Renée Audette. Proulx ran unsuccessfully for the Prescott seat as an Independent Liberal in 1921 but was elected to the provincial assembly two years later, defeating Gustave Évanturel, the official Liberal candidate. In 1929, he was named a judge for Sudbury district.