Archaeological work done mainly in the 1980s shows that Kosrae was definitely settled by the early first millennium A . D ., although future research is expected to push this date back to the first millennium B . C . The society was highly stratified at the time of initial contact with the West. In aboriginal times, Kosrae shared many common cultural features with surrounding islands, including: matrilineal lineages and clans; social rank defined by affiliation with kin groups defined as "noble" or "commoner"; noble control over land worked mainly by commoners; elaborate redistributive exchanges; and settlements oriented around a group of close relatives sharing access to a single cook house. For several decades after their 1824 discovery by Europeans, Kosraens were victimized by whaling crews, who made deals with chiefs for the Island's abundant foods, water, and female companionship. The first missionary established a station in 1852 and Virtually the entire population was Christianized in the 1870s. During the Japanese mandate of 1914-1945, extensive Economic development occurred, run by and for the benefit of the Japanese companies and government. The United States was granted control over Micronesia at the end of World War II. After two decades of relative neglect, in the 1960s the U.S. administration poured in money for education, health care, public works, and development projects. Employment with the government became and remains the major source of jobs and cash income, spent on food, building materials, vehicles, and other imports. Most Kosraens continue to acquire the bulk of their subsistence from traditional crops and fishing, but imports have replaced almost all other native manufactures.