Chia-i, shih (municipality) and seat of Chia-i hsien (county), on the western coastal plain of Taiwan. It lies at the foot of the A-li Mountains, on Taiwan’s main north–south rail and highway routes. Narrow-gauge branch railways built by the Japanese (who occupied Taiwan from 1895 to 1945) run from Chia-i to the sugar-producing plains to the west and into the A-li Mountains for the transport of lumber. Because of its excellent position as a communication centre, Chia-i has developed into a rice market and a centre of trade.
Chia-i’s importance was increased between 1920 and 1930 by the completion of the Chia-nan irrigation system, which waters a large area in the plain between Chia-i, the administrative centre of the system, and T’ai-nan to the south. Lumbering is practiced in the region, and in consequence Chia-i has become a papermaking and plywood-manufacturing centre. It also has wineries and plants producing tires, cement, and alcohol. Junior colleges offer vocational training in agriculture, education, commerce, and technology. Area 23 square miles (60 square km). Pop. (2008 est.) 273,075.