Born in Summerfield, Prince Edward Island, the son of Peter Sinclair, he was first elected to the House of Commons of Canada in the Prince Edward Island riding of Queen's in 1917 federal election. A Liberal, he was re-elected in 1921. He was defeated in 1925 but was re-elected in 1926.
Born in Summerfield, Prince Edward Island, the son of Peter Sinclair, he first won a seat in the House of Commons of Canada in 1917 as the representative for Queen's riding in Prince Edward Island. He was a Liberal and re-elected in 1921. However, he lost his seat in 1925 but regained it in 1926.