Chinese cities of the Song period became some of the largest in the world, owing to technological advances and an agricultural revolution. Kaifeng, which served as the capital and seat of government during the Northern Song (960–1127), had some half a million residents in 1021, with another half-million living in the city's nine designated suburbs. By 1100, the civilian population within the city walls was 1,050,000; the army stationed there brought the total to 1.4 million. Hangzhou, the capital during the Southern Song (1127–1279), had more than 400,000 inhabitants during the late 12th century, primarily due to its trading position at the southern terminus of the Grand Canal, known as the lower Yangzi's "grain basket." During the 13th century, the city's population soared to approximately a million people, with the 1270 census counting 186,330 registered families living in the city. Although not as agriculturally rich as areas like western Sichuan, the region of Fujian also underwent a massive population growth; government records indicate a 1500% increase in the number of registered households from the years 742 to 1208. With a thriving shipbuilding industry and new mining facilities, Fujian became the economic powerhouse of China during the Song period. The great seaport of China, Quanzhou, was located in Fujian, and by 1120 its governor claimed that the city's population had reached some 500,000. The inland Fujianese city of Jiankang was also very large at this time, with a population of about 200,000. Robert Hartwell states that from 742 to 1200 the population growth of North China increased by only 54% percent in comparison to the Southeast which grew by 695%, the middle Yangzi Valley by 483%, the Lingnan region by 150%, and the upper Yangzi Valley by 135%. From the 8th to 11th centuries the lower Yangzi Valley experienced modest population growth in comparison to other regions of South China. The shift of the capital to Hangzhou did not create an immediate dramatic change in population growth until the period from 1170 to 1225, when new polders allowed land reclamation for nearly all the arable land between Lake Tai and the East China Sea as well as the mouth of the Yangzi to the northern Zhejiang coast.