Medcalf was born in
Delgany,
County Wicklow, Ireland, in 1803 and moved to
Upper Canada in 1819 with his parents, William and Martha Medcalf, and seven siblings. They lived on the
Big Otter Creek in
Bayham, Ontario. In 1823, Medcalf relocated to
Philadelphia in the United States, where he began working as a
blacksmith and
millwright. He married Mary Harrison in Philadelphia before returning with her to Canada in 1839 to run several
foundries in
Toronto; they had four sons and two daughters together. He opened the Don Foundry and Machine Shop in 1847, which specialized in the production of agricultural machinery and
steam engines. ==Political career==