In early American history, prior to western expansion approximately 60 million Buffalo (Bison) roamed the Great Plains. They traveled from the north boarder of the now called United States to the southern boarder into Mexico. This was believed to be one of the largest group of mammals living together on the planet. They were a primary source of the way of life to the tribes that lived amongst them. As western expansion continued; by the year 1800 there no buffalo found east of the Mississippi River. Around the 1830’s the railroad was heading deep into the plains and the mass killing of buffalo began. People were encouraged to kill the buffalo by the rail company and the US military in or to control the Native American population. During this period roughly 20 thousand people were hunting buffalo decimating them, estimated at 8000 kills per day. By 1883 less than 300 buffalo were left in North America; approximately 50 were left in the United States. As of today, there are around 500,000 buffalo found in the U.S. most of these are not pure Buffalo (Bison), because they have been cross bread with other live stock. Out of the 500,000 thousand only 30,000 are consider wild, living on wild life reserves.