John Hays Hammond, JR. John Hammond was one of the greatest electrical and mechanical inventors of his time. The things he invented during his lifetime impacted history a great deal. According to John Pettibone, John Hays Hammond, Jr. was born in 1888 in San Francisco, California (Pettibone 1). Most of his life Hammond was known as Jack. He was the second son and namesake of a world-famous mining engineer, who was the friend, confidant, and almost running mate of William Howard Taft. Jack’s father