Since the Three Kingdoms period, Nanjing has been an industrial centre for textiles and minting owing to its strategic geographical location and convenient transportation. During the Ming dynasty, Nanjing's industry was further expanded, and the city became one of the most prosperous cities in China and the world. It led in textiles, minting, printing, shipbuilding and many other industries, and was the busiest business center in East Asia. Textiles boomed particularly in Qing dynasty, the industry created around 200 thousand jobs and there were about 50 thousand satin machines in the city in 18th and 19th century.