This broad, wooded bay was the site of one of the most productive sugar plantations on St. John [1]. Par Force, as the estate was called, was owned by the Rif family. The name Reef Bay is a corruption of this name; it has nothing to do with coral.
There are sugar mill ruins at the edge of the bay. They are marked by NPS signs explaining the sugar production process. The old sugar factory here is also home to a rare species of bats—look up when you step inside.
Most people get to Reef Bay by hiking (the only other alternative is by boat). On the trail down, you pass several other sugar mill ruins and the foundation of an old worker’s cottage. The Reef Bay Great House is a short detour off the Lameshur Bay Trail. The old great house is one of the largest on St. John, but it’s in disrepair, and the National Park Service does not encourage visits here.
Links:
[1] http://www.moon.com/destinations/virgin-islands/st-john