Between 1866 and 1890 more than four million head of cattle were trailed through Fort Worth which was soon known as “Cowtown”. For the drovers heading longhorn cattle up the Chisholm Trail to the railheads, Fort Worth was the last major stop for rest and supplies. Beyond Fort Worth they would have to deal with crossing the Red River into Indian Territory. At the height of World War I in 1917, the Fort Worth Stockyards was the largest horse and mule market in the world. Military officers from Allied countries came to purchase the animals to support their war efforts. In 1989 the North Fort Worth Historical Society opened the Stockyards Museum in the Exchange Building which now hosts many thousands of visitors from all over the world each year.