He attended the common schools. He graduated from Albany Medical College in 1859, and practiced medicine in Waverly.
During the American Civil War he was an army surgeon from 1862 to 1865 with the 109th New York Volunteers. Afterwards, he resumed the practice of medicine in Waverly. He died on December 16, 1912, at his home in Waverly, of pneumonia.
Johnson was a presidential elector in 1888, voting for Benjamin Harrison and Levi P. Morton. And a member of the New York State Senate (38th Doctorate) from 1896 to 1900, sitting in the 119th, 120th, 121st, 122nd and 123rd New York State Legislatures.