This article explores the role played by an influential family, the Pan-ch'iao Lin Penyuan clan, in the development of northern Taiwan mountain areas during the Ch'ing period. Chinese migrants penetrated into Taiwan mountain areas on an expanding scale during the first half of the eighteenth century. Influential families played an important role in the frontier opening venture. Some succeeded while others failed. The frontier policies in the Ch'ing period can be divided into three stages. In the first stage, the Ch'ing government maintained a rigid boundary between the Han and aboriginal people, restricting the Han people to one side of the boundary and the aborigines to the other. This was known as "hua-chieh feng-shan" (demarcation and territorial segregation) policy. During this period, Lin P'ing-hou, the founder of the Pan-ch'iao Lin Pen-yuan clan in Taiwan, started to invest in the mountain area after his retirement from an official post in Kuang-his province. Around 1828-29 he moved his family from Hsin-chuang (in Taipei county) to Ta-ko-k'an (Ta-his of T'ao-yuan county) with an eye to reclaiming the wasteland in the mountain area. His two sons, Kuo-hua and Kuo-fang, carried on the venture after his death in 1844. However hard their efforts had been, the reclamation work made only little progress and they were even forced to move back to the lowland area at Pan-ch'iao (in Taipei county). The reasons for the setback are various. The lack of official protection against the threats of mountain aborigines is probably the main reason, though poor agricultural conditions are certainly another factor. The second stage took place when the government played the main role in opening the mountain area. This began in 1875 after the Japanese invasion of southern Taiwan. During this period, the effort to reclaim the mountain area made only little progress in spite of government encouragement and military support, which involved large spendings and high costs of human lives. The main reason is that influential families of Taiwan were not successfully motivated to take part in risky investment without being entrusted with sufficient power and privileges In the third stage, after Taiwan was established as a province in 1885 when the Sino-French war ended, Liu Ming-ch'uan, the first provincial governor, started a large-scale frontier-opening and pacification project. He adopted a policy of official-gentry cooperation, entrusting political power and economic privileges to some influential families, such as the Pan-ch'iao Lin Pen-yuan clan and the Wufeng Lin clan. As Lin Wei-yuan of the Pan-ch'iao Lin Pen-yuan clan was appointed Assistant Administrator for Pacification and Frontier-opening (Fu-k'en pang-pan), he had both power and interest to put the policy into practice thoroughly. As a result, the new land was reclaimed, and camphor processing and tea growing were expanded. Northern Taiwan became so prosperous that it soon surpassed southern Taiwan to become the new economic center. Therefore, it can be said the official-gentry cooperation policy launched by Governor Liu Ming-ch'uan and the influential clans such as Lin Pen-yuan contributed a great deal to the success of mountain development project in the Ch'ing period.