Clayco Inc., a development firm with $820 million in annual revenue, is moving its headquarters to Chicago. Founder and chairman Bob Clark, who moved to Chicago in 2010, said St. Louis will remain integral to the business, and none of Clayco’s approximately 700 employees in St. Louis will be laid off. The company will have about 280 employees in Chicago, a number it expects to double over the next couple of years. St. Louis will remain the home of Clayco’s Concrete Strategies division and its Forum Studio architectural practice. The company’s accounting and IT operations also will stay in St. Louis.