MacPherson was born at Grande Anse on Cape Breton Island on April 16, 1891. He was raised on his parents' farm and was sent to be educated in Richmond and Pictou. After graduation, he taught school for a brief period until he raised enough money to attend law school at Dalhousie University. In 1913 he established a law practice in Swift Current. MacPherson enlisted in the Canadian Expeditionary Force in 1916, and was wounded in 1917. After the war, he was appointed solicitor to the Soldier Settlement Board, which helped demobilized soldiers homestead. MacPherson established a law practice in Regina. In 1921 he challenged Liberal William Motherwell in the riding of Regina but lost. MacPherson was successful as a Conservative in the 1925 provincial election. Upon re-election in 1929, MacPherson became Attorney General in the Anderson government. He negotiated the transfer of natural resource rights from the federal government to the province. As the Depression began to take hold, MacPherson took on responsibility for the increasingly difficult portfolio of Provincial Treasurer. In 1934, MacPherson was defeated, along with all other members of the Anderson government. After a brief federal appointment, MacPherson returned to his law practice in Regina. He ran for the leadership of the federal Conservative Party in 1940 and 1942, finishing second on both occasions. After World War II, he represented the Saskatchewan's CCF government as legal counsel in its attempts to stop the railways from circumventing the Crow's Nest Pass agreement. In 1959, Prime Minister John Diefenbaker appointed MacPherson to the Royal Commission that examined railway and freight rate problems in the country. MacPherson lost again in the 1960 provincial election. In 1961 he was named a bencher of the Law Society of Saskatchewan and received an honorary doctorate from the University of Saskatchewan. He continued to practice law until his death on June 11, 1966.