He was born in Florenceville, New Brunswick, the son of Andrew Cunningham Caldwell and Margaret Wakem, and, after completing his education, became a farmer there. Caldwell was married twice: to Annie Abeldt in 1892 and later to Melissa Haladay. He was president of the United Farmers of New Brunswick and served on the executive board of the Farmer's Co-operative Company of New Brunswick. Caldwell was first elected to the House of Commons in a 1919 by-election held after Frank Broadstreet Carvell was named chairman of the Board of Railway Commissioners. He was defeated when he ran for re-election in 1925. Caldwell went to England as a farm delegate to protest an embargo on Canadian potatoes. He died in Ottawa at the age of 69.
