The Americans had less difficulty finding a variety of different products to barter for tea. The Empress of China and the following early vessels were able to use ginseng and some species to secure tea. Yet, the market for ginseng was rather small, so the Americans began trading furs with Indian tribes in the American Northwest, which was in turn traded for species in Guangzhou, which was then used to purchase tea. From 1790 to 1812 supplies of furs and then sealskins were depleted and new products had to be found as demand also waned. In the Pacific Islands, merchants evaded cannibals and traded with natives to get sandalwood and sea slugs that could be traded for species. But those items soon ran their course, and by 1814 species had risen to nearly 70% of total American exports. In the 1820s, they attempted to compete with the British opium trade that monopolized the Indian crops by trading for Turkish opium. Massachusetts General Hospital, McLean Hospital and the Boston Athenæum, the Bunker Hill Monument, many factories, mines, the US's first railroad, university buildings, high schools, public libraries, and an orphanage were built with the proceeds of opium smuggling. The opium trade allowed the US to transfer China's wealth to fuel the industrial revolution.