The State Barrier Fence of Western Australia, formerly known as the Rabbit-Proof Fence, the State Vermin Fence, and the Emu Fence, is a pest-exclusion fence constructed between 1901 and 1907 to keep rabbits, and other agricultural pests from the east, out of Western Australian pastoral areas. There are three fences in Western Australia: the original No. 1 Fence crosses the state from north to south, No. 2 Fence is smaller and further west, and No. 3 Fence is smaller still and runs east–west. The fences took six years to build. When completed, the rabbit-proof fence (including all three fences) stretched . The cost to build each kilometre of fence at the time was about $250 (). When it was completed in 1950, the No. 1 Fence was the longest unbroken fence in the world. History Rabbits were introduced to Australia by the First Fleet in 1788, but they became a problem after October 1859, when Thomas Austin released 24 wild rabbits from England for hunting purposes, believing "The introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting." The rabbits proved to be extremely prolific and spread rapidly across the southern parts of the country. Australia had ideal conditions for an explosion in the rabbit population, including the fact that they had virtually no local predators. By 1887, losses from rabbit damage compelled the New South Wales Government to offer a £25,000 reward () for "any method of success not previously known in the Colony for the effectual extermination of rabbits". A Royal Commission was held in 1901 to investigate the situation. Construction The fence posts are placed apart and have a minimum diameter of . There were initially three wires of gauge, strung , , and above ground, with a barbed wire added later at and a plain wire at , to make the fence a barrier for dingoes and foxes as well. Wire netting, extending below ground, was attached to the wire. The fence was constructed with a variety of materials, according to the local climate and availability of wood. At first, fence posts were made from salmon gum and gimlet, but they attracted termites (locally known as white ants) and had to be replaced. Split white gum was one of the best types of wood used in the fence. Other timbers used were mulga,