Iron-hulled sailing ships represented the final evolution of sailing ships at the end of the age of sail. They were built to carry bulk cargo for long distances in the nineteenth and early twentieth centuries. They were the largest of merchant sailing ships, with three to five masts and square sails, as well as other sail plans. They carried lumber, guano, grain or ore between continents. Later examples had steel hulls. They are sometimes referred to as "windjammers" or "tall ships".[1] Several survive, variously operating as school ships, museum ships, restaurant ships, and cruise ships.[2]