Fort Frederik stands at the waterfront in Frederiksted, the smaller of St. Croix's two main towns. The fort was built in 1760 and named after the Danish crown prince; it's smaller and less elaborate than Fort Christiansvaern in Christiansted, but its historical significance is arguably greater. This is the site where Danish Governor Peter von Scholten proclaimed the emancipation of enslaved people in the Danish West Indies in 1848 — one of the earlier formal emancipations in the Caribbean, though it came under the duress of an imminent rebellion.
The fort now operates as a museum run by the Virgin Islands government, with exhibits on the 1848 emancipation, the 1878 labor rebellion (which began in Frederiksted), and the general history of the Danish colonial period. The museum is modest but the building itself is worth visiting, and the ramparts offer a good view of the Frederiksted waterfront and the cruise ship pier. Frederiksted receives fewer visitors than Christiansted, and the town has a quiet, slightly melancholy atmosphere that's very different from the busier east end — worth a half-day.