Ben-Gurion was the first Prime Minister of the State of Israel and its leading political voice for the country’s first decade. In 1930, he formed Mapai, the Zionist Labor Party, and in 1935 he became chairman of the Executive Committee of the Jewish Agency for Palestine. He emphasized the development of the Negev as a key to Israel’s growth. Ben-Gurion declared the State of Israel on May 14, 1948. As leader of the new country, he oversaw the development of institutions and established Jerusalem as the capital.