In 1889, while Nebraska was engaged in a debate over statewide prohibition, Johnson posed as an anti-Prohibitionist to obtain information from brewery and saloon owners.

Johnson's temperance activities earned him governmental notice and he was appointed special agent of the Department of the Interior to enforce laws in Indian Territory and Oklahoma in 1906.

He was chief agent of the United States Indian Service from July 1908 until September 1911 and secured more than 4,400 convictions through a practice of sweeping into gambling saloons and other disorderly places.

On 13 November 1919, he was captured by a mob of medical students while at a speaking engagement at Essex Hall and paraded through the streets of London on a stretcher before being rescued by police.

In April 1921, Johnson was booed into silence at Toronto's Massey Hall and at a rally in downtown Windsor while campaigning for tightening Ontario's prohibition laws.