Completed in 1849, the original Wadjemup Lighthouse (also known as Rottnest Island Light Station) was Western Australia's first stone lighthouse and was built to provide a safer sailing passage for ships to Fremantle Port and the Swan River Colony. A second and larger replacement tower was built on the same site in 1896. It is the fourth oldest extant lighthouse in Western Australia and was Australia's first rotating beam lighthouse. A shipwreck that was partly caused by poor communications and misunderstood signals from the lighthouse prompted the construction of another lighthouse on the island in 1900. Location selection and obelisk Rottnest Island is the largest and northernmost of several islands near the Port of Fremantle. It is from the mouth of the Swan River and is generally the first land sighted by ships arriving from the west. The island is long and at its widest point, with a total land area of . The lighthouse site is at the highest point of the island, on Wadjemup Hill, with the tower base above sea level. It is west of the Thomson Bay settlement and about south-west of the Geordie Bay settlement. Between 1837 and 1843, Commander John Clements Wickham led an expedition in with Lieutenant John Lort Stokes to chart sections of the Australian coastline. During the voyage, Fremantle was visited seven times and in the course of one of these visits on 25 March 1840, Stokes wrote in his journal: "We moved the ship to Rottnest Island, to collect a little material for the chart and select a hill for the site of a lighthouse. The one we chose lies towards the South east end of the island bearing N76°W (true) twelve miles and a quarter from the ." In October 1840, Surveyor-General John Septimus Roe, together with Wickham and Stokes published Sailing Directions for the Navigation About Rottnest Island. The document appeared in the Government Gazette and included: "Rottnest Island ... may now be distinguished from the mainland and Garden Island by a white obelisk, 15ft in height, with a pole in the middle, of the same length, which has recently been erected on its highest part near the centre of the island. This sea-mark, being elevated about 157ft above sea level, may be seen from a ship's deck in clear weather at the distance of 7 or 8 leagues, and will shortly give place to a lighthouse of