Canyon in 1989 led to the creation of the ConAgra Foods campus. Several nearby buildings, including the Nash Block, have been converted into condominiums. The stockyards were taken down; the only surviving building is the Livestock Exchange Building, which was converted to multi-use and listed on the National Register of Historic Places. A historic preservation movement in Omaha has led to a number of historic structures and districts being designated Omaha Landmarks or listed on the National Register of Historic Places. Much of the push toward preservation came after Omaha gained the notorious designation of having, in 1989, demolished the largest-ever National Register historic district in the United States, a record that still stands as of 2013. The Jobbers Canyon Historic District, along the Missouri River, was felled for a new headquarters campus for ConAgra Foods, a company which threatened to relocate if Omaha did not allow them to raze the city's historic district. The Jobber's Canyon warehouses had before then been allowed to deteriorate and were the scene of several fires set by the homeless population that had come to live in the abandoned buildings. At the time, there were no plans in place for revitalizing the buildings. In the 1980s and 1990s, Omaha also saw major company headquarters leave the city, including Enron, founded in the city in 1930 and taken to Houston in 1987 by the now-notorious Kenneth Lay. First Data Corporation, a large credit-card processor, also was founded in Omaha in 1969; as of 2009, its headquarters are in Atlanta. Inacom, founded in Omaha in 1991, was a technology company that customized computer systems for large businesses, and was on the Fortune 500 list from 1997 until 2000, when it filed for bankruptcy. Northwestern Bell, the Bell System affiliate for Northwestern states, had its headquarters in Omaha from its founding in 1896 until it moved to Denver in 1991 as US West. Level 3 Communications, a large Tier 1 network provider, was founded in Omaha in 1985 as Kiewit Diversified Group, a division of Kiewit Corporation, a Fortune 500 construction and mining company still headquartered in Omaha; Level 3 moved to Denver in 1998. World Com was founded by a merger with Omaha's MFS Communications, started as Metropolitan Fiber Systems in 1993. MFS, backed by Kiewit Corporation CEO Walter Scott and Warren Buffett, purchased UUNET, one of the largest Internet backbones in the world, for $2