Clergyman, lecturer, reformer, was born in Springfield, Ohio, the son of John Andrew and Edith Jane (Brelsford) Dinwiddie. After attending the public schools of Springfield, in 1884, he entered Wittenberg College, in the same town. Financial difficulties, howevre, interrupted his work several times and delayed his graduation until 1894. That same year he was licensed as an Evangelical Lutheran Minister; in 1901 he was ordained. On November 8, 1894, he married Olive Hannah Smith at Emporia, Kansas and they had two children: Horace Milton and Edith Rowena.

Although Dinwiddie was an ordained minister, he held no pastorate but devoted his mature life to the movement for temperance reform. While in college he toured Ohio in this cause and was president of the Young Men's Prohibition League of the state in 1888. Between 1890 and 1892 he was secretary of the state executive committee of the Prohibition party, and during the next five years he was successively grand counselor, grand electoral superintendent of the Ohio branch of the International Order of Good Templars (a temperance organization, and lobbyist of the Ohio Anti-Saloon League. In 1897 he became state superintendent of the Pennsylvania Anti-Saloon League, and two years later moved to Washington D.C., to be the first legislative superintendent of the American Anti-Saloon League. In 1907 he gave up his post because of a disagreement with the national superintendent, but returned to it in 1911. He resigned in 1920 because of differences with Wayne B. Wheeler [q.v.]. who, as general counsel, was nominally subordinate to Dinwiddie but was usurping a good deal of authority. Until his death, however, Dinwiddie was one of the conspicuous figures in the campaign in support of legislation both in Congress and in the states to restrict the traffic of alcoholic beverages and to prohibit their manufacture and sale throughout the nation. In behalf of these reforms he lectured extensively and published many articles and booklets. He possessed a rare talent for dealing with public men, combining tact and diplomacy with high idealism and a spirit of fairness and tolerance of opposing views; he had, also, outstanding ability as an organizer. His knowledge of the legislative progress of prohibition was as comprehensive as that of any man of his time. From the start he succeeded in obtaining definite results, not by upheavals or mere combative arguement, but by the presentation of the cause of prohibition as a humane and practical program of legislation.

Though he was most closely affiliated with the Anti-Saloon League, he was a dominating figure in a considerable number of other temperance societies, including the powerful International Order of Good Templars. For more than thirty years he headed the temperance work of the Evangelical Lutheran Church, continuing after it had combined with the United Lutheran Church, and from 1994 until his death he was superintendent of the National Temperance Bureau in Washington, comprising numerous organizations. He served also on the executive committees of the World Prohibition Federation and the World League against Alcoholism and the permanent committee of the International Congress against Alcoholism, of which he was president in 1920-21. He was the official delegate of the United States Government to five meetings of the International Congress against Alcoholism, held in Europe cities between 1909 and 1923, and was chairman of the one which met in Washington in 1920. In these, as well as in the other national and international meetings of the many organizations to which he belonged, he exercised a dominating influence.

The first definite fruits of his labors in the national field came in 1901 when he was largely responsible for the passage of the law abolishing beer and liquor in the army canteen and for the appropriation of the $5,000,000 for recreational centers at army posts. Subsequently, he participated in the campaign preceding the passage of some thirty temperance laws by Congress, the most important of which were the Webb-Kenyon interstate liquor shipment law and the prohibition enforcement act, popularly called the "Volstead Act." He played a signigicant part, also, in securing the adoption of the 18th Amendment to the Constitution. At the time of his death he was busily engaged in organizing a campaign for a renewal of the fight in Congress for national prohibition. He suffered a heart attack in July 1934, from which he never recovered, and died at his home in Washington, He was buried in Springfield, Ohio.

(Justin Stewart, Wayne Wheeler, Dry Boss (1928): Am. Issue (Westerville, Ohio). May 1935; Lutheran, May 23, 1935; Who's Who in America, 1934-36; Evening Star (Washington) May 6, 1935.)