It is widely known that Taiwan's modern economic growth began during the early Japanese colonial period, which implies that the growth rate of per capita GDP increases significantly in the early 20th century. Using the available estimates from various studies, we compile a long-term series of Taiwan's GDP, and show that the per capita GDP in the beginning of the 20th century was about the level of a traditional agricultural economy. Using an indirect method of estimation, we also show that the per capita GDP growth rate during the Ching era is close to zero. The above results based on the long-term GDP data are then shown to be consistent with the data in demographic change, body height change, rice yields, and population-land area ratios.