The hum of construction equipment serves as background noise most afternoons as people visit Mercado San Agustin or the MSA Annex. The sound of a construction project in the works is nothing new for people who have lived just west of Interstate 10 near Congress Street or who frequent the area for shopping and dining. Since 2008, the Gadsden Company has been developing the Mercado District on what was once barren land on the growing west end of downtown Tucson.