Question

What invention was a major contributor to the end of the open range on the great plains

Answer 1

One factor was barbed wire. As farmers and ranchers wisened up, they used the wire to fence in their cattle, destroying the use of cowboys, and taking away one aspect of the "wide open west".  Herds of cattle took over the plains and destroyed the grass. In 1883 the big drought struck and water streams dried up and prairie fires grazed. Also the barbed wire and the natural disasters.