By the end of the 18th century the population had risen to 300 million from approximately 150 million during the late Ming dynasty. The dramatic rise in population was due to several reasons, including the long period of peace and stability in the 18th century and the import of new crops China received from the Americas, including peanuts, sweet potatoes and maize. New species of rice from Southeast Asia led to a huge increase in production. Merchant guilds proliferated in all of the growing Chinese cities and often acquired great social and even political influence. Rich merchants with official connections built up huge fortunes and patronized literature, theater and the arts. Textile and handicraft production boomed.