 The irrigation project, creating Medina Lake, was built by 1500 skilled workers who worked in shifts operating 24 hours a day to complete the dam in two years.Medina County is part of the San Antonio, TX Metropolitan Statistical Area.The county is named after the Medina River, which was named in 1689 after the Spanish cartographer Pedro de Medina by the Spanish explorer Alonso de Leon, the first European to encounter the river.