Yanchang County (simplified Chinese: 延长县; traditional Chinese: 延長縣; pinyin: Yáncháng Xiàn) is a county under the administration of the prefecture-level city of Yan'an, in the northeast of Shaanxi Province, bordering Shanxi Province across the Yellow River to the east.

[2] Yanchang County contains the following seven towns:[1][2] Located on the Loess Plateau,[2] the county's terrain is largely hilly, with a low point of 470.6 metres (1,544 ft) above sea level, and a high point of 1,383 metres (4,537 ft) above sea level.

[1] Human activity in Yanchang County can be traced back thousands of years, and the first administrative district in the area arose in 266 AD.

[1] Communist forces would retain control of the county during the rest of the Civil War, as well as during the Japanese Invasion of China.

[1] The county has vast deposits, mainly of petroleum, coal, natural gas, and salt.

[5] In 2000, the county government launched reforms meant to boost its productivity, and in 2005 the company had merged into the Yanchang Oilfield Company Ltd.[5] After merging into Yanchang Oilfield, the county's oil production further expanded, achieving a stable annual output of approximately 250,000 tons from 2005 through 2010.

[1] The county's natural gas reserves total 2,000 square kilometres (770 sq mi) in area, and 100 billion cubic meters in volume.