Born on a farm near Stryker, Ohio, Kniffin attended the public schools and then studied law.

He was admitted to the bar in 1919 and commenced practice in Napoleon, Ohio.

Kniffin was elected as a Democrat to the Seventy-second and to the three succeeding Congresses (March 4, 1931–January 3, 1939).

Following the end of his term, he resumed the practice of law.

This article incorporates public domain material from the Biographical Directory of the United States Congress