Tungning era, the previous economy monopoly system developed during the Dutch Formosa continued to be practiced. Qing dynasty When the Qing Dynasty annexed Taiwan, they established the Kavalan sub-prefecture in Yilan. In 1806, armed conflicts broke out among various ethnic immigrants, followed by pillaging by pirates. The Qing Dynasty government subsequently realized that if they continued to disregard the Kavalan people and did not establish rule of law and a system of defense, Yilan would become a haven for criminals and outlaws, a thorn in the side for Taiwan. In 1809, Jiaqing Emperor incorporated Kavalan into the domain of the empire. Troops were dispatched to quell pirate attacks and chart local territory. Local government systems in Taiwan underwent many changes during the Qing Dynasty period. But with regards to administrative levels lower than the county, including local villages, there were no major changes. The earliest organization and planning of Yilan consisted of seven citadels. In 1835, the seven citadels were further divided into 12 citadels based on the needs of the changing population and environment. This arrangement remained unchanged until the end of Qing Dynasty rule. After the Mudan Incident in 1874, Qing rulers changed their passive attitude and took a more ambitious approach in ruling Taiwan. The original aboriginal term Kavalan district was renamed with a more Han-centric Yilan name and the administrative system was also changed accordingly from the original temporary "district" to a formally governed "county". In 1875, the newly created Taipeh Prefecture included modern-day Yilan County. Empire of Japan After the First Sino-Japanese War in 1894, the Qing government handed over Taiwan to Japan in accordance with the Treaty of Shimonoseki. Modern-day Yilan County covers , , and as they existed from 1920 to 1945, all under Taihoku Prefecture, during Japanese rule. Republic of China After the handover of Taiwan from Japan to the Republic of China in October 1945, the present-day area of Yilan County was incorporated under Taipei County. On 10 October 1950, Yilan County was established as a county of Taiwan Province with Yilan City as the county seat. Geography Yilan County sits on the Yilan Plain, a combined alluvial plain created by Lanyang River and other minor streams with a rough shape of triangle. On the three vertices of the triangle sit the Toucheng, Sanxing and Su-ao Townships with a roughly equal distance of 30 km on the three sides. The Xueshan