They raised them on ranches. Today there are more buffalo than there have been in 100 years. Many Indian tribes are raising buffalo on their land. Ranchers like buffalo because buffalo are hardier than cattle. They can stand outside in howling blizzards and stay alive by eating only grass.
Ranchers sell buffalo for meat.
You can buy the meat in some grocery stores. It tastes like beef. Raising buffalo can be good for the land. Buffalo chew down old grass and their hooves stir up the soil, so new grass and native plants grow the way they did on prairies hundreds of years ago. Buffalo once ranged from Alaska into Mexico.