The U.S. ship PLYMOUTH ROCK was built in East Boston, Massachusetts, by Donald McKay for George B. Upton and Capt. Eben Caldwell, of Boston, and was launched on 13 February 1849. 973 tons; 156/168/178 x 36.5 x 21.5 feet (length of keel/deck/overall x beam x depth of hold).

The PLYMOUTH ROCK was intended for Enoch Train & Co's White Diamond Line of packets between Boston and Liverpool. 5 March 1849, maiden voyage, Boston-Liverpool, under Capt. Caldwell. On 5 February 1851, the PLYMOUTH ROCK, under Capt. Caldwell, sailed from Boston, arriving off Cork on 19 February, a record run of 12 1/2 days. On 18 February 1853, the PLYMOUTH ROCK, under Capt. Caldwell, sailed from Boston for Victoria, Australia, arriving at Melbourne on 19 May (entered in 20 May), with 90 passengers; under the command of Capt. F. Tucker, she cleared Melbourne on 13 August (sailed 18 August) for Callao (where she arrived on 23 September) and the Chincha Islands, where she loaded a cargo of guano.

In 1856, the PLYMOUTH ROCK was acquired by Grinnell, Minturn & Co for their Red Swallowtail Line of packets between New York and Liverpool. She was re-registered at New York on 29 April 1856. The PLYMOUTH ROCK served on the Red Swallowtail Line until the line ceased operations in 1880, when she was sold Norwegian. During this period her westbound passages averaged 37 days, her shortest voyage being 22 days, her longest 45 days. She was still afloat and in service in 1891.

Sources: William Armstrong Fairburn, Merchant Sail (Center Lovell, Maine: Fairburn Marine Educational Foundation, [1945-1955]), vol. 2, pp. 105, 1124, 1171, 1190, 1196, 1197, 1212, 1213, 1279, 1300; vol. 4, pp. 2350, 2649, 2664; vol. 5, pp. 2904, 2949, vol. 6, pp. 3650, 3813, 3854-3856; Marten A. Syme, Shipping Arrivals and Departures; Victorian Ports, vol. 2: 1846-1855, Roebuck Society Publication No. 39 (Melbourne: [Roebuck Society], 1987), p. 168; Robert Greenhalgh Albion, Square-riggers on Schedule; The New York Sailing Packets to England, France, and the Cotton Ports (Princeton: Princeton University Press, 1938), pp. 282-283; Forrest R. Holdcamper, comp., List of American-flag Merchant Vessels that received Certificates of Enrollment or Registry at the Port of New York, 1789-1867 (Record Groups 41 and 36), National Archives Publication 68-10, Special Lists 22 (Washington, DC: National Archives and Records Service, 1968), p. 562.