Prince Frederick, the county seat of Calvert County, is an unincorporated Census‑Designated Place. The Prince Frederick post office is located at 35 Duke Street, Prince Frederick, MD 20678.
In 1882, 14 of the 18 structures that comprised Prince Frederick burned, including the courthouse, resulting in the loss of all court and land records.
Prior to its selection as the county seat in 1722, the land on which the courthouse would be built was known as Williams Old Field.
The town was most likely named for King George the Second's son, Frederick, who was Prince of Wales at the time the town was first established. [en.wikipedia.org, accessed September, 2012]