William “Bill” Raynor Mackay was born on November 12, 1911, in Tenafly, New Jersey, son of Malcolm Sutherland Mackay Sr. and Helen Raynor Mackay. He had three siblings, Malcolm “Bud” Mackay, Donald “Pete” Mackay, and Mary Ellen Wang (née Mackay). As a young man, he attended Berkshire School and later Williams College, both in Massachusetts. In 1937, he married Joyce Selleck Childs, daughter of Alfred DeForest Childs and Mrs. Ernest (Theodora) Stauffen Jr., in Englewood, New Jersey. Together the couple had three children, Julie Childs Snell (née Mackay), Helen Kampfe (née Mackay), and William R. Mackay Jr.

In 1935, William Mackay (and later Joyce Mackay) moved to his family’s ranch, the Lazy E-L Ranch, in Roscoe, Montana. The Lazy E-L Ranch was primarily a cattle operation that expanded to 13,000 acres over the years. Mackay helped run the ranch with George Wright, a veterinarian, until 1942 when Wright left to form his own vet practice.

Mackay frequently corresponded with family, particularly his older brother, Malcolm “Bud” Mackay Jr., who worked as a managing partner at Mackay & Co., a New York-based stock company, and later as director of Northwest Airlines, and his younger sister, Mary Ellen Wang (née Mackay).

In 1950, William Mackay campaigned for and was elected as a state representative from Carbon County in the Montana Legislature. He served on the finance and appropriations committees during his tenure as state representative, and he was also appointed to the Commission on Reorganization in the State of Montana, chaired by Senator Glen Larson, which operated from 1951 to 1953. In 1952, Mackay began his campaign for state senator and was elected in 1953, where he served until 1972.

Additionally, in 1952, the Mackay family offered their collection of Charles Russell artworks to the Montana Historical Society for a sum of 50,000 dollars. Malcolm S. Mackay Sr. was a longtime friend of Russell and a collector of his work. The collection included fifteen large oil paintings, seven bronzes, and numerous watercolor and ink sketches and was appraised at approximately 300,000 dollars. Dr. K. Ross Toole, Director at the Historical Society, spearheaded the six-month fundraising campaign, receiving aid or donations from several organizations. Toole successfully raised the 50,000 dollars needed to purchase the collection and, in December 1952, the Russell collection was packaged and shipped from Billings, MT to MTHS. Mackay was appointed to the Montana Historical Society Board of Trustees in 1951 where he remained until 1961, and he served on the board again from 1981 until 1996.

One of Mackay’s most notable accomplishments as a state senator was assisting in the development of the Montana Legislative Council. In 1951, an interim committee, designed to study state government and make recommendations, suggested the creation of a legislative council. This governmental body could make inquiries, conduct investigations, and provide assistance, including drafting of bills, to state legislators in and in between the biennium sessions. In 1953, Mackay, along with other legislators, put forth the Montana Legislative Council act, which was passed and signed into law. Mackay served as chairman of the council during this time. The act was later struck down by the Montana Supreme Court as unconstitutional in January 1954 in a three-two decision, cited reasons being the council’s extended term outside the legislative session, pay for the committee, and its subpoena powers.

The Legislative Council act was passed into law a second time in 1957 and was held up as constitutional by the Montana Supreme Court in August 1957. The council had twelve members serving on it, including Mackay, who later served as chairman from 1961-1962. The Legislative Council was tasked with analyzing the state government for opportunities to consolidate departments, eliminate unnecessary activities, increase efficiencies, and study the problems related to the collection of taxes. In 1961, the Council was empowered to carry out studies related to the reorganization of Montana state government and fiscal procedures.

Mackay also served as the chairman of the Legislative Audit Committee. This committee, along with the position of legislator auditor, was created by Senate Bill 2, sponsored by Mackay, and was signed into law by Governor Tim Babcock during the 1967 session. The Legislative Audit Committee was granted the authority to audit state agencies and ensure that their fiscal operations were carried out appropriately. Mackay served on this committee until 1971.

In addition to politics, William Mackay was involved in a variety of organizations, including the Montana Stockgrowers Association, an organization established in 1884 to help protect ranchers and cattlemen from predators, disease, and rustlers. He was first elected to the executive committee in 1949 and later served as second Vice-President in 1964, first Vice-President in 1965, and as President from 1967 to 1969. Mackay worked closely with Ralph Miracle, who served at various times as the secretary and president of the Stockgrowers Association, to discuss pertinent bills and the Stockgrowers’ position on them. Mackay gave numerous speeches at annual conventions and county meetings, often speaking on legislative issues that pertained to ranchers or cattlemen, including government reapportionment and beef imports.

During Mackay’s last session as state senator, in 1971, the Montana Legislature put the question of a sales tax to the public. The issue remained unresolved, and the legislature had a special session in the summer of 1971, where they passed a referendum to be given to the people to vote on in the fall of 1971, where the people voted it down.

Mackay also opposed reapportionment, a decision passed down from the United States Supreme Court case Baker v. Carr in 1962, which caused significant legislative redistricting and increased the political power of urban areas while reducing the influence of rural ones. Mackay argued this case limited rural Montanan’s representation in the legislature and, consequently, did not run for reelection in 1972, after reapportionment reduced his term from four years to two years.

Mackay served on a variety of boards of directors, including the Carbon County Memorial Hospital, the Red Lodge Music Festival, Koal Krudes Inc., Colorado Rocky Mountain college, among others. He remained active in an assortment of organizations until the mid-1990s. William Mackay died on December 6, 1999, at the age of 88. He was buried at Roscoe Cemetery in Roscoe, Montana.