Blenheim may have been launched in 1776 in Philadelphia as Britannia. By 1777 she was the Massachusetts-based privateer American Tartar and had taken several prizes. She had also participated in an inconclusive single-ship action with a British merchantman. The British Royal Navy captured American Tartar late in 1777 and she became HMS Hinchinbrook. The Royal Navy sold her in 1783 and she became the West Indiaman Blenheim. In 1785-86 she became a Greenland whaler and she continued in that trade until two French frigates captured and burnt her in 1806. American privateer The vessel's exact origins are obscure. Lloyd's Register (LR) described her as originating in Philadelphia in 1776. The Register of Shipping gave her origins simply as "BrPlant", i.e., British Plantations (British colonies), in 1777. Granville Hough stated that the vessel American Tartar had been Britannia, out of New York, but then had become a privateer with a letter of marque from Massachusetts. Commander John Grimes commissioned American Tartar on 29 November 1776. Her owners were Dean and Joseph Barrell, and other investors. On 21 May 1777, American Tartar sailed in company with two American frigates, and for a cruise in the North Atlantic. American Tartar parted from the two frigates shortly thereafter and sailed for northern European waters. On her way, American Tartar captured the 150-ton (bm) brigantine Sally and sent her into Boston where she was libeled on 17 July. American Tartar encountered the British merchantman Pole, Maddock, master, on 12 July at (or ). Pole was sailing from New York to Liverpool with 40 crew and passengers. American Tartar approached and opened fire. Maddock so maneuvered Pole as to be able three times to clear American Tartars forecastle. After almost three and a half hours, American Tartar withdrew. Pole, of sixteen 6-pounder guns, had sustained a passenger and two mates wounded. The next day American Tartar captured two brigs off the Shetland Islands. The first was carrying lumber and hides. The Americans took out her hides and tackle and furnishings, and then burnt her. The second brig was carrying tar. The Americans kept her with them. On the 15th, American Tartar captured Royal Bounty, of 300 tons (bm), William Kerr, master. She had been sailing from Greenland to Leith. Grimes put a prize crew aboard her, as well as the hides taken from the first brig captured the previous day, and 30 barrels of tar from