Yan Mountains in the context of "Northeast China"

Northeast China (Chinese: 东北; pinyin: Dōngběi) is a geographical region of China, consisting officially of three provinces Liaoning, Jilin and Heilongjiang. The heartland of the region is the Northeast China Plain, the largest plain in China with an area of over 350,000 km (140,000 sq mi). The region is separated from the Russian Far East to the north and east by the Amur, Argun and Ussuri Rivers; from North Korea to the south by the Yalu and Tumen Rivers; and from the neighboring North China to the west by the Greater Khingan Range and Yan Mountains. It is also bounded by the Bohai Bay and Yellow Sea to the southwest, about 100 km (62 mi) away from East China's Jiaodong Peninsula across the Bohai Strait, due to be connected via a proposed undersea tunnel.

The four prefectures of Inner Mongolia (which is part of North China) east of the Greater Khingan, i.e. Chifeng, Tongliao, Hinggan and Hulunbuir, are sometimes also considered broader parts of Northeast China, and together with the aforementioned three provinces formed what was historically known as Inner Manchuria, in contrast to the Outer Manchuria (or "Outer Northeast" in Chinese literatures) annexed by the Russian Empire during the mid-19th century.

The Shanhai Pass (simplified Chinese: 山海关; traditional Chinese: 山海關; pinyin: Shānhǎi Guān; lit. 'Mountain Sea Pass') is a major fortified gateway at the eastern end of the Great Wall of China and one of its most crucial fortifications, as the pass commands the narrowest choke point in the strategic Liaoxi Corridor, an elongated coastal plain between the Yan Mountains foothills and the Bohai Sea, which is the only easily traversable landway between North and Northeast China. It is located in present-day Shanhaiguan District, Qinhuangdao, Hebei province, on the east bank of the Shi River, with defensive walls stretching from the Yan Mountains all the way to the shores of the Liaodong Bay.

Throughout Chinese history, garrisons around the pass served as frontline defensive outposts against raids and incursions into the North China Plain by various non-Sinitic ethnic groups from the Northeast (also known as Manchuria since the 19th century), including the Dongyi, Donghu (Xianbei and Wuhuan), Khitan and Jurchen (Manchus). The current Shanhai Pass was built during the early Ming dynasty as the easternmost fortification of the Ming Great Wall, and was extensively reinforced after Yongle Emperor moved the capital from Nanjing to Beijing following the Jingnan campaign, making it the most important defensive barrier in all of China, as it shielded the heartland region around the imperial capital. The pass' strategic location dictated that without mounting a costly direct siege, the only way an invading army can get past the pass' defense was to circumvent it around the north through a few treacherously narrow mountain passes deep within the Yan Mountains, which would make it very difficult to maintain supply lines and thus any sizeable invasions. This defensive significance therefore earned the pass the famous nickname "Greatest Pass Under Heaven" (天下第一关).

The Sixteen Prefectures, more precisely known as the Sixteen Prefectures of Yan-Yun (traditional Chinese: 燕雲十六州; simplified Chinese: 燕云十六州; pinyin: Yānyún Shíliù Zhōu) or the Sixteen Prefectures of You-Ji (Chinese: 幽薊十六州; pinyin: Yōujì Shíliù Zhōu), were a historical region in North China that comprises present-day Beijing, Tianjin and parts of northern Hebei and Shanxi provinces. Situated around the Yan Mountains along the Great Wall, it was a strategic gateway region into the Central Plains and thus marred by constant military conflicts between various states for centuries since the end of the Tang dynasty until the establishment of the Yuan dynasty.

The Donghu (/ˈdʊŋˌhuː/; simplified Chinese: 东胡; traditional Chinese: 東胡; pinyin: Dōnghú) were a tribal confederation of nomadic Hu people that were first recorded from the 7th century BCE and were taken over by the Xiongnu in 150 BCE. They lived in northern Hebei, southeastern Inner Mongolia and the western part of Liaoning, Jilin and Heilongjiang along the Yan Mountains and Greater Khingan Range.

Qinglong Manchu Autonomous County (Chinese: 青龙满族自治县, Manchu: ᠨᡳᠣᠸᠠᠩᡤᡳᠶᠠᠨ ᠮᡠᡩᡠᡵᡳ ᠮᠠᠨᠵᡠ ᡠᡴᠰᡠᡵᠠ ᡯᡳᡷᠶ ᡥᡳᠶᠠᠨ) is a Manchu autonomous county in northeastern Hebei province, China, bordering Liaoning Province to the north and east and located in the eastern part of the Yan Mountains. It is under the administration of the prefecture-level city of Qinhuangdao, and, as of 2004, had a population of 520,000 residing in an area of 3,309 km (1,278 sq mi). Bordering county-level divisions are: Lingyuan and Jianchang County (Liaoning) to the north, Liaoning's Suizhong County and Qinhuangdao city proper to the east, Qian'an and Lulong County to the south, and Kuancheng Manchu Autonomous County and Qianxi County to the west.

During the 1976 Tangshan earthquake 180,000 buildings in Qinglong collapsed, but no fatalities occurred.

Tangshan (Chinese: 唐山; pinyin: Tángshān) is a coastal, industrial prefecture-level city in the northeast of Hebei province. It is located in the eastern part of Hebei Province and the northeastern part of the North China Plain. It is located in the central area of the Bohai Rim and serves as the main traffic corridor to the Northeast. The city faces the Bohai Sea in the south, the Yan Mountains in the north, Qinhuangdao across the Luan River to the east, and Tianjin to the west.

Much of the city's development is thanks to the industrialization, beginning in 1870, when Kailuan Group established coal mines in the region. It is the birthplace of China's first standard-gauge railway, the first railway plant, the first steam locomotive, and the first cement factory. It was hailed as China's "cradle of industrialization". Even today, Tangshan is a hub of steel, energy, chemical, and ceramics production. Ping opera, which originated from the city's Luanzhou county, is one of the five most popular Chinese operas.