USS Monongahela pictured c1864, was a barquentine–rigged screw Sloop-of-War that served in the Union Navy during the American Civil War. Her task was to participate in the Union blockade of the Confederate States of America.
A sloop of war by Richard B. Spencer
A two-Decker and a Brig sloop of war - National Maritime Museum
Configuration of typical brig-sloop. In the 1770s, the two-masted sloop re-appeared in a new guise as the brig sloop. The successor to the former snow sloops, brig sloops had two masts while ship sloops continued to have three (since a brig is a two-masted, square-rigged vessel and a ship is a square-rigger with three or more masts, though invariably only three in that period).
Early in 1845 sloop USS Portsmouth braved turbulent waters at tip of South America & headed north up west coast.Captain John B.Montgomery under orders to patrol off San Francisco Bay as part of US Pacific Fleet effort to prevent Britain from acquiring California.When war broke out Montgomery sailed into bay & sent marines to Yerba Buena.Little resistance since John C.Fremont slipped across bay & disabled Mexican cannon.American flag 1st flew over town July 9,1846.Today Portsmouth Square.