In the period prior to European contact, the Yapese had extensive relationships with the other island groups in the Region. Yapese sailors traveled from Yap to Palau where courageous men quarried stones in the Rock Islands to be carted back to Yap and utilized for ceremonial exchanges. People in the eastern villages in Gagil had extensive relationships with Carolinean sailors from Ulithi, Fais and other atolls to the east. These sailors came to Yap particularly during times of food shortage and typhoon crises in the atolls and Yapese often sailed with them back to their home islands. With the entrance of European traders into the area as early as 1526, Yapese continued their exploration of the surrounding Islands in the company of European sailors. It was in this early period that European diseases spread from Guam, resulting in devastating epidemics. In 1872, David O'Keefe arrived in a Chinese junk and immediately set up a copra and trepang trade. He transported large Yapese stones from Palau in Exchange for payment in copra and trepang. Yap was officially colonized by both Spain and Germany in 1885. Carrying their dispute to the pope, Germany achieved sovereignty over the island, and the Spanish were allowed to continue their Religious work to convert the Yapese to Christianity. The German era ended in 1914 when the Japanese navy seized control of Yap. Japanese development projects on Yap proved to be of little economic value, but as World War II neared, they constructed military bases, including troop garrisons and two airfields. During this period, the Yapese attended a five-year school in Japanese language and culture; the most promising students were sent to craft schools on Palau where they studied agriculture, carpentry, nursing, mechanics and other practical occupations. In 1944, the United States bombed Yap, and at the end of World War II the U.S. Navy set up an occupation government that lasted until June 1951. The United States Trust Territory of the Pacific Islands was formally established in 1951, and Yap was one of six districts in the trust territory. During this era, the U.S. government emphasized education and political development among the islanders. The Yap Islands Congress first convened in May 1959 and established the foundation for Yap State, which was formally organized in 1978. In 1964, the Yap High School was opened and American contract teachers were hired to staff it. By 1980, Yapese fully controlled the state and local governments and administered their schools and churches. Many Yapese men and women today are graduates of colleges and universities in the United States and hold positions of leadership in the economic, educational, and political life of the islands. Yap State is now part of the Federated States of Micronesia, which also includes the states of Truk, Pohnpei, and Kosrae.