The stockyards at Omaha closed in 1999, and are now a labarynth of collapsing corrals and pens. In the 1960's this was the largest livestock center in the world, filled with thousands of animals on trading days, and surrounded by meatpacking plants. It surpassed the more famous Union Stockyard in Chicago as the busiest stockyard in 1955, when nearly 43,000 cattle passed through the yard in a single day. The industry trend of moving the slaughterhouses closer to the cattle feedlots, led by companies like IBP (whilch was purchased by Tyson in 2001), led to the demise of this and other stockyards, and changed the ecomomy of the meatpacking cities like Omaha, Chicago, and Kansas City. In Omaha, trading was centered at the Livestock Exchange Building, a romanesque brick tower that, now empty, still looms above the stockyards, awaiting redevelopment.