The diocese of Chiayi covers 2,442 square kilometers and includes Chiayi city and the counties of Chiayi and Yunlin.
Chiayi city covers 60 square kilometers and has a population of 273,967 as of July 2008. There are 5 parishes in the city.
Chiayi county covers 1,901 square kilometers and has a population of 549,002 as of July 2008. The 20 parishes there cover 2 cities, 2 towns and 14 villages in the county.
Yunlin county covers 1,290 square kilometers and has a population of 724,994 as of July 2008. It comprises one city, five towns and 14 townships, and has 19 parishes.
Chuloshan, the ancient name of Chiayi, was given from two sources: one phonetically resembled the tribe name Tirosen, and the other came from a semantic utterance indicating "Mountains surround in the East."
Chuloshan was once the foothold of early immigrants from mainland China dated back to the early 17th century. The present name was awarded by Emperor Chien-Lung of the Qing dynasty in 1787 for praising the citizens' loyalty.
Chiayi, is located on the plains of Taiwan about 30 kilometers from the coast and 202.5 kilometers southwest of the capital Taipei.
Mandarin Chinese is the official language of Taiwan. However, at least half the population prefers to speak Taiwanese at home, especially for those living in the southern region. Taiwanese, or the "Minnan" dialect, originated from Fujian province of mainland China. Minnan means "south of the Min River." Many elderly people also understand Japanese as a result of the 1895 -1945 occupation of Taiwan by Japan. Taiwan's 10 aboriginal tribes each have its own language. These languages bear no relation at all to Chinese, and are generally regarded as Malayo Polynesian in origin.
Chiayi is located adjacent to the tropic of cancer, characterized by the subtropical monsoon climate. The city has an average temperature of 23.3 degrees Celsius.
A majority of the population of Chiayi city and Yunlin county is engaged in the service sector (70 percent), while Chiayi county is famous of its fruit plantation