On 24 December 1951, Libya declared its independence as the United Kingdom of Libya, a constitutional and hereditary monarchy under King Idris, Libya's only monarch. The discovery of significant oil reserves in 1959 and the subsequent income from petroleum sales enabled one of the world's poorest nations to establish an extremely wealthy state. Although oil drastically improved the Libyan government's finances, resentment among some factions began to build over the increased concentration of the nation's wealth in the hands of King Idris.