Area coe 305 was the single original area code in the state of Florida, and still currently serves all of Miami-Dade County and the part of Monroe County that is in the Florida Keys. The area code is also overlaid by area code 786, but only in Miami-Dade County and not in the Keys portion of Monroe County; the mainland portion of Monroe County is served by area code 239. Due to this overlay, mandatory 10-digit calling is required for the Miami-Dade County portion of the area code, but not for the Florida Keys.