Changzhou (Chinese: 常州) is a prefecture-level city in southern Jiangsu province of China. It was previously known as Yanling, Lanling, Jinling, and Wujin. Located on the southern bank of the Yangtze River, Changzhou borders the provincial capital of Nanjing to the west, Zhenjiang to the northwest, Wuxi to the east, and the province of Zhejiang to the south. Changzhou is part of the highly developed Yangtze Delta region of China extending from Shanghai going northwest, which now has more than 36,000,000 inhabitants. Its total population was 4,592,431 inhabitants at the 2010 census whom 3,290,918 lived in the built-up area made up of 5 urban districts.The agglomeration is now part of the Suzhou-Wuxi-Changzhou metropolitan area which has now more than 36,000,000 inhabitants, only second in China after the Pearl River Delta Economic Zone.
"The Ruins of Yancheng" (淹城遺址), comprise the remains of a walled city located in the Wujin district of Changzhou that was founded over 3000 years ago at the beginning of the Western Zhou dynasty. The earliest record of a settlement on the site of modern Changzhou is as a commandery founded in 221 bc at the beginning of the Qin Dynasty. During the interregnum between the Sui and Tang, the city of Piling (毗陵) was the capital of Shen Faxing's short-lived Kingdom of Liang (ad 619 to 620). Changzhou got its present name meaning "ordinary prefecture" in 589. Following construction of the Grand Canal in 609, Changzhou became a canal port and transshipment point for locally-grown grain, and has maintained these roles ever since. The rural counties surrounding Changzhou are noted for the production of rice, fish, tea, silk, bamboo and fruit.
During the Taiping Rebellion of the 1850s, one of five palaces housing the leaders of the so-called "Kingdom of Celestial Peace" was constructed in Changzhou. Today the ruins of the "King's Palace" can be found near the People's No.1 Hospital.
In the 1920s, Changzhou started to attract cotton mills. The cotton industry got a boost in the late 1930s when businesses began relocating outside of Shanghai due to the Japanese occupation. Unlike many Chinese cities, Changzhou continued to prosper even during the upheavals of the Cultural Revolution of 1966–76. Today it is an important industrial center for textiles, food processing, engineering (diesel engines, generators, transformers and other machinery), and high technology.
Changzhou has a wide range of temperature differences throughout the year.