1956-1992 The interstate highway system bypassing previously established travel routes. This kills the business of diners, gas stations, and motels that previously serviced travelers.
1980s Hypermarts and supercenters. The ease of transportation of goods across the country put local small businesses into competition with larger businesses based thousands of miles away. Why go to local stores when Walmart has everything in one place? Profits that once stayed in the local economy with local business owners are now funneled far away.