but could rely upon outsourcing for its steamship engines. Companies which would build marine engines for Lawrence & Foulks prior to the Civil War included leading firms such as the Allaire Iron Works, Morgan Iron Works, Henry Esler & Co. and the Novelty Iron Works. After the war, when many of New York's marine engine manufacturers went out of business, Lawrence & Foulks appears to have come increasingly to rely upon New Jersey's Fletcher, Harrison & Co. to meet its machinery requirements. As with other shipbuilders of the era, the size of Lawrence & Foulks' workforce could fluctuate greatly depending upon the available work. The company appears to have employed about 50 people for every ship under construction, and it was capable of building as many as four ships at once. Early years, 1850s–1860 Through the 1850s, Lawrence & Foulks built a number of steamers and other vessels for South American clients, including the 300-ton Spanish steamers General Concha and General Serrano for Cuban service; a large steamer for the Río de la Plata; and two small high-pressure riverboats for the Peruvian government destined for service on the Amazon. Two 1,300-ton steamers for Californian service were also completed. In 1855, Lawrence & Foulks completed construction of the Long Island Sound steamer Commonwealth. Setting a new standard of elegance for Sound steamers, this large, lavishly outfitted steamer quickly became a favorite with the travelling public. In 1859–60, Lawrence & Foulks built the fast oceangoing steamships and , sister ships designed for passenger-cargo service between New York and New Orleans. Both vessels were later purchased by the U.S. Navy and would serve with distinction during the Civil War as gunboats. American Civil War, 1861–65 With the outbreak of the Civil War, the U.S. Navy quickly purchased or chartered hundreds of ships from private steamship companies, which were needed to establish the blockade of Confederate ports and to transport troops and supplies along the Atlantic coast. The steamship companies were then obliged to return to the shipyards to replace their fleets, only to find themselves vying with the Navy which needed still more ships. The strong demand for new shipping created boom conditions for American shipyards which would last to the end of the war. New York shipyards in this period also benefited from the Treaty of Tianjin. Ratified in 1860, the treaty gave U.S. companies increased access to Chinese waterways and ports,