[2] His parents, George and Mary Coates, emigrated to the United States in 1881 and initially settled in Pittsburgh, Pennsylvania.

He married Sadie B. Pearce on October 14, 1890, and a daughter, Hazel Marie, was born on February 1, 1893.

Coates was elected Lieutenant Governor of Colorado on a fusion ticket, having received the nominations of the Democratic, Populist and Silver Republican parties.

A shooting war was triggered when one of the strikers, believed to have been unarmed, had been shot through the throat by a deputized mine guard.

In spite of intense pressure from others, Coates helped to persuade the governor not to send the Colorado National Guard.

In 1911, he was elected city commissioner for public works on the socialist ticket and served in this role until 1914.