John Grigsby was born in Sioux Falls, South Dakota.
[1] Grigsby graduated in 1903 from the University of South Dakota College of Law.
He practiced law in Sioux Falls and served in the United States Army during World War I, attaining the rank of captain.
In addition, Grigsby served on the board of directors of the state veterans home.
[2] As lieutenant to Governor William J. Bulow, Grigsby's main function was to preside over the South Dakota Senate.