In the year 1700 A.D., immense herds of bison lived in this area, and between 30 and 60 million roamed North America until the mid 1800s. Their removal began as settlers moved into the Midwest, with some killed by farmers protecting crops and others hunted by fur trappers and traders. After the railroad connected the coasts, the slaughter became even easier, supplying markets for bison tongue as a delicacy, bones for fertilizer, and hides for tanneries, while the rest was left to rot. Most herds were destroyed in the 1870s and 1880s, and by 1884 only 325 wild bison remained. Bison were essential to prairie health because their grazing spread plant seeds, their hooves opened the soil for sprouting, and they ate small saplings that might otherwise have grown into trees shading out prairie species. A few herds remain, including one of 1,200 in Custer State Park, and Native tribes, including the Omaha and the Ponca, are taking a leadership role in the bison's recovery. For the indigenous people living here, the bison was more than a source of food, because nearly every part could be used to provide shelter, clothing, food, and tools for daily living.