Born in Perth, Canada West, Motherwell attended the Ontario Agricultural College, graduating in 1881; then worked that summer in Portage la Prairie, Manitoba. The following year he spring he returned to the prairies joining settlers in who traveled by rail to Brandon, Manitoba, then by red river cart and wagon beyond to the area of Abernethy, Saskatchewan, where he settled and constructed the Motherwell Homestead. In 1901, he co-founded and became president of the Territorial Grain Growers' Association. He served in the provincial legislator from 1905 to 1918, Saskatchewan Minister of Agriculture from 1906-1917. His resignation from the provincial legislature was in protest over the provincial Liberal Party's support for conscription and reduction in French language rights.