Born in Perth, Ontario, Motherwell moved to Abernethy as a young man. For the rest of his life he worked in the cause of the western farmer. In 1901 he initiated the Territorial Grain Growers' Association, the parent of subsequent provincial associations which led to improvements in the inspection and shipment of grain. Minister of agriculture for Saskatchewan (1905-1918) and for Canada (1921-1926; 1926-1930), he established an agricultural college at the University of Saskatchewan and aided in creating the Saskatchewan Co-operative Elevator Company.