It was developed as early as the end of Qing Qianlong, and in the first year of Xianfeng (185 1), Wang discovered coal mines here and formed a residential area. Because there are mountains in the local area, the two peaks protrude like breasts, hence the name Milk Mountain. 1946, Naizishan sub-district, 1955, and 1959, changed to Naizishan commune; 1983, Naizishan Town resumed. 1989 abolished Naizishan Town and set up Naizishan Street and Zhonggang Street. 1997, Naizishan street covers an area of 56.2 square kilometers and has a population of 20,000. It has jurisdiction over Guangming, Qianjin, Yong 'an, Dong Jian, Limin, Shangshan, Xinfeng, Tiebei, Qian Jing, Dairy and other 10 neighborhood committees, as well as Kouqin, Hongsheng, Industry, Construction, Xinli, Anle, Youlian, Wanbao and Nanjian. With an area of 5.7 square kilometers and a population of 29,000, Zhonggang Street governs Unity, Chunguang, Dongkang, Dongshun Donggang, Yuxin, Chaoyang, Zhengyang, Xinmin, Dongsheng, Xiangyang, Lixin, Zhenxing, Yuwen, Xinhua, Limin, Le Tong, Xigang, Shengli, Yongsheng, Yongan, Peace, Peace, Nangang, Tongxin and Peace. 1At the end of 1997, the villages under the jurisdiction of the urban sub-district offices were adjusted. In 2000, Zhonggang Street was abolished and merged into Naizishan Street. Naizishan Street used to be the former site of Jiaohe Coal Mine (declared bankrupt in 2002 due to resource exhaustion). In 2005, the area was 6 1.84 km2, the population was 156 1 household, and 4 1427 people. It governs 4 communities, 10 administrative villages, 38 residents' committees and 22 natural villages. In 2005, seven villages including Xinli, Anle, Hongsheng and Kouqin were placed under the jurisdiction of Henan Street. In 2007, the total population was 29,360, of which the urban population was 2,6771person and the rural population was 2,589.