It was subsequently settled intermittently by sealers and whalers in the early 19th century, and from 1836 on a permanent basis during the British colonisation of South Australia.

Kangaroo Island separated from mainland Australia around 10,000 years ago, due to rising sea level after the last glacial period.

[8] A mainland Aboriginal dreaming story tells of the Backstairs Passage flooding:[9] "Long ago, Ngurunderi's two wives ran away from him, and he was forced to follow them.

[14] At least two contemporary accounts (Taplin 1867, Bull 1884) report reputed crossings of Backstairs Passage from Kangaroo Island to the mainland by kidnapped women seeking to escape from their captors.

'A fine specimen of her race' was pointed out to J. W. Bull as having swum the passage in 1835,[15] and a woman and her baby were found dead on the beach after a presumed crossing in 1871.

The greatest loss of life occurred with the wreck of Loch Sloy on 24 April 1899 at Maupertuis Bay, when 31 people were drowned, and one initial survivor subsequently perished.

It was later suggested that Kingscote could serve as the capital of South Australia, but the island's resources were insufficient to support such a large community, so the settlement of Adelaide was chosen.

Traditionally, sheep grazing has been the key element in agriculture on the Island; however, in recent times, more diverse crops, such as potatoes and canola, have been introduced.

The Florance vineyard was established under supervision of B. Hayes, who produced its first wine – Eastern Cove Cygnet – and introduced it at the University of South Australia in 1990.

The American Bee Journal, 25 November 1885, stated "Several pure colonies were reared from this one, [the first hive from Queensland] and two of them were sent to Kangaroo Island, where they appear to thrive well."

In the South Australian Advertiser, 7 March 1884, Bonney stated "About three weeks ago I divided the original colony, and the Chamber of Manufactures now possesses three good swarms of Ligurians; two of these will probably be ready to send out towards the end of the month."

From the South Australian Advertiser, 1 August 1884 "On June 25 the original hive of Ligurian bees, imported by the chamber from Queensland, was sent safely to Mr Turner, at Smith's Bay, Kangaroo Island.

[38] Among these was Kangaroo Island Council,[39] due to its large land area, extensive road network, low population and high tourism visitation.

Kangaroo Island is connected to the main South Australian power grid by a pair of 33 kV subsea cables across Backstairs Passage.

[48] Following withdrawal from service of Karatta, RW Miller operated the MV Troubridge, in later years as a joint venture with the South Australian Government.

Seventy-five sheep and cattle died on the inaugural trip due to carbon monoxide poisoning, and the ship was once described as 'steering like a shopping trolley'.

SeaLink now holds a virtual monopoly on sea transport to Kangaroo Island, primarily due to its long term lease of the Cape Jervis berth.

Following the withdrawal of ASA, Kendell Airlines (another Ansett subsidiary), operated 19-seat Fairchild Metroliners and 34-seat SAAB aircraft to the Island.

Upon Ansett's ultimate demise in 2002, Regional Express (Rex) acquired the Kendell aircraft and continued services to Kingscote Airport until early 2020, when it ceased operation citing competition from Qantas[58] In competition with the larger aircraft, and generally with more flexible timetables, a succession of smaller airlines from the 1970s tried with varying success to maintain a 'second string' presence.

Island Air and Pagas operated briefly in the 1970s, whilst the most successful, Emu Airways, commenced in 1980 and made its final flight in November 2005.

And also, because of their ability to spread livestock diseases such as Sarcocystis and Toxoplasmosis, a program to eradicate an estimated population of between 3,000 and 5,000 cats within 15 years was started in 2016.

The idea of a cull of the burgeoning koala numbers is distasteful to the public, and the state government prefers to use sterilisation for population control.

These include a helipad in the island's south-western wilderness,[76] a southern bluefin tuna pen on the north coast of the island[77] (which resulted in the withdrawal of the proposal), The Cliffs Golf Resort near Pennington Bay (for which Crown land was considered for private sale or lease to developers)[78] and a port proposal at Smith Bay to facilitate timber exports[79] and cruise ship visitation.

[81][82] Kangaroo Island has been identified by BirdLife International as an Important Bird Area (IBA) because it supports populations of the vulnerable fairy tern, the near threatened bush stone-curlew, hooded plover and western whipbird, and the biome-restricted rock parrot and purple-gaped honeyeater.

[85][86] She described the population utilizing the limestone caves at Ravine de Casoars as "innumerable" and described watching "dozens" come ashore at Sandy Beach.

Before being contained on 16 December 2007, over 20% of the Island had been burnt, totaling 900 square kilometres (220,000 acres), principally within National Park and Conservation Reserves.

[93] A number of wildlife species, some unique to Kangaroo Island and some already endangered before the 2019–2020 bushfires, might be facing extinction in the wild as a result of the fires.

The site is also the source of magnificent specimens of trilobites such as Redlichia takooensis, Emuella polymera, Balcoracania dailyi, Megapharanaspis nedini, Holyoakia simpsoni, and Estaingia (=Hsuaspis) bilobata.

The Emu Bay Shale in contrast, appears to represent deposition in restricted basins on the inner shelf, indicating that soft tissue preservation occurred in a range of environmental settings during the Cambrian.

Pleistocene fossilised footprints indicate extinct Australian megafauna, such as diprotodons, short faced kangaroos, and thylacines were once distributed on the island.