 The 538,136 tons registered in foreign trade in 1831 had increased to 1,047,454 in 1847 and to 2,496,894 in 1862, a figure which represented the culmination of our ship-building tonnage until surpassed in WW I.From 1848 to 1858 ship building had been maintained at an average of 400,000 tons a year.This construction was caused by two conditions, the development of the clipper ship after 1845 and the increased demand for shipping.