The mine was most productive between 1875 and 1920, when the average mined in a year was . Records show that in 1910, North Skelton was forwarding four full freight trains per day to the smelters on south Teesside. In 1929, the assets of Bolckow, Vaughan and Co, were acquired by Dorman, Long & Co. The second owners held the mine until January 1964, when it was closed. After closure, the site was used for various above-ground industrial concerns. Between 1876 and 1949, 36 men died in the mine through various accidents such as crushing injuries, roof falls, explosions and limbs being removed by passing trains. There were even recorded instances of boys dying after they had trespassed on the site.