From Wikipedia, the free encyclopedia. Catheys Valley (formerly, Cathay and Cathey's Valley) is a census-designated place in Mariposa County, California. It lies in Catheys Valley 22 miles (35.2 km) northeast of Merced, and 8 miles (13 km) southwest of Mariposa, at an elevation of 1325 feet (404 m). As of the 2010 census, Catheys Valley had a population of 825. Catheys Valley was named after Andrew Cathey, a native of North Carolina, who settled in the valley around 1850. The ZIP Code is 95306. The community is inside area code 209.