sentences:  In 1910, 20,000 animals arrived at the Stockyards each day from farms and ranches in 20 states, including Nebraska, Colorado, Wyoming, Idaho, Montana, Utah and South Dakota.Ten slaughterhouses and meatpacking plants were in operation.Between 1907 and 1910, most of the original pens were rebuilt with walkways, allowing buyers to view stock without walking through the pens.