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 in 1907, the rabbit-proof fence (including all three fences) stretched 2,023 miles (3,256 km). The cost to build the fences at the time was about £167 per mile ($250/km).
When it was completed in 1907, the 1,139-mile (1,833 km) No. 1 Fence was the longest unbroken fence in the world. It has been claimed that the fence is visible from space; however, similar claims about the larger Great Wall of China have been debunked by NASA.
Rabbits were introduced to Australia by the First Fleet in 1788 and they became a problem when Thomas Austin released 24 wild rabbits for hunting purposes in October 1859, saying that "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 were extremely prolific creatures and spread rapidly across the southern parts of the country. Australia had ideal conditions for a rabbit population explosion.
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 to investigate the situation in 1901.
The fence posts are placed 12 ft (3.7 m) apart, and have a minimum diameter of 4 in (100 mm). There were initially three wires of 12½ gauge placed at 4 in (100 mm), 1 ft 8 in (0.51 m), and 3 ft (0.91 m) above ground, with a barbed wire added later at 3 ft 4 in (1.02 m) and a plain wire at 3 ft 7 in (1.09 m) to make the fence a barrier for dingoes and foxes as well. Wire netting was placed on this, which extended to 6 in (150 mm) below ground.