Ballast Key is an island in the Florida Keys in Monroe County, Florida, United States. It is the southernmost point of land in the contiguous United States. It was the last privately owned land within the boundaries of the Key West National Wildlife Refuge. Tennessee Williams often painted canvases while visiting David Wolkowsky on Ballast Key in the late 1970s and early 1980s. Ballast Key features a main house with four bedrooms and a master suite, and a fully equipped three-bedroom guesthouse overlooking a palm tree-lined sand beach. Water is supplied to the homes by desalination.