Grandmaster Chen Xiaowang has been known to prefer a green tea sometimes known as Mao Jian Cha (信阳毛尖茶). It is typically produced in Henan Province (red area below).
That’s not much use in terms of limits as Henan Province is a big place – 167,000 square kilometers (= 64,479 square miles) or about the size of the US states of Florida or Wisconsin. Henan Province has likely over 96 million people by now, which places it ahead of nations like Egypt and Vietnam.
The typical administrative hierarchy in a Chinese province is prefecture-county-township-village. Henan Province is divided into 17 prefectures and one sub-prefectural city, Jiyuan (yellow highlighted area). The latter usually means that the city is directly administered by the province as opposed to by its containing prefecture. The famed Chen family village, Chenjiagou, is located in Jiaozou (#4 above – in the center along the top border). From the point of view of Mao Jian tea we are primarily interested in Xinyang Prefecture (#14 in the lower right above) with an area of 18,908 square kilometers (7300 square miles) – about the size of the US state of New Jersey – and a population approaching 6,500,000.