With an area of 310,403 square miles and a population (est. 1972) of 60 million, Pakistan adjoins Iran, Afghanistan, India and the Arabian Sea. Pakistan became a sovereign nation in 1947, when the British Empire of India was partitioned into two countries - India and Pakistan. At first a dominion, Pakistan declared itself a republic in 1956. It is a land of rugged mountains and river valleys, where irrigation aids agriculture, the occupation of 80% of its people. The Indus River flows for some 1,000 miles from the base of the Himalayas to the Arabian Sea and with its tributaries supplies reservoirs, canals and hydroelectric plants. The capital city is Islamabad.