Before the mid-1800s, much of the American West was a vast expanse of open plains. Native tribes followed buffalo herds unimpeded for hundreds of miles, cowboys ran cattle wherever water and grass led them, and the cattleman's Law of the Open Range ruled. All this changed when settlers pouring into the West under the Homestead Act of 1862 brought with them the Eastern farmer's concept of fencing in farms. With the invention and mass production of barbed wire in the 1970s, it soon became possible for homesteaders to fence off millions of acres of what was once open range. But barbed wire threatened the livelihood of the cattlemen who depended on unfenced grasslands, and a clash of cultures was inevitable.