William Mercer Owens Dawson was born in Bloomington, Maryland. At the age of ten, he began his public education at Cranberry (now Terra Alta), Preston County, where he subsequently earned an apprenticeship as a cooper. From 1873 to 1891, he was owner and editor of the Preston County Journal. Dawson entered politics as a state senator in 1881 and served two terms. As chair of the Republican state executive committee, he gained notoriety as the architect of the party's tax reform plan. In 1895, he served as Clerk of the House of Delegates, and in 1897, he became secretary of state under Governor George W. Atkinson.
During Dawson's term, the legislature increased the powers and duties of the state tax commissioner and gave the governor the right to remove tax assessors for refusal to comply with new tax laws. In 1909, state educational, charitable, penal, and correctional institutions were reorganized under a board of control. Although the legislature approved Dawson's election reform bill, it rejected his proposals for the environment, a pure food and drug act, workers' compensation, and the creation of a public service commission.
After his term as governor, Dawson served on the Virginia Debt Commission, the Board of Control, and the Public Service Commission. Dawson died in Charleston in 1916.