This island is approximately 115 km (71 mi) south of Bird Islet, a part of the east end of the Wreck Reefs.

The coral reefs are built on the top of a large shield volcano, produced by eruptions of the Tasmantid Seamount Chain.

The area was visited by increasing numbers of whalers during the off season in New Zealand, in search of the wintering humpback and sperm whales[4] in the middle of the 19th century.

[5] Denham reported that in July 1863 the islets had only two or three plants, including a bush 3–4 m (9.8–13.1 ft) high, and were frequented by sea turtles weighing 60–100 kg (130–220 lb).

On 12 October 1858, Denham reported that Cato Island was more substantial than other cays in the area, measuring 1⁄3 by 1⁄6 mile (0.54 by 0.27 km), rising to 19 feet (5.8 m), and covered in coarse tufted grass, Rottboilla; a creeping plant, Nyctagin portulaca; and a sort of buttercup Senebiera crucifera, undermined and fertilised by burrowing mutton birds, the only species that the sailors chose to eat.

When they returned with plants from the Percy Isles and seeds from Sydney to provide succour for castaways in August 1859, Denham again reported that the birds formed a cloud hovering 60 feet (18 m) above the island, though "a few visits like ours would tend to check the accumulation in proportion to each boat bringing off upwards of 100 dozen eggs at a three hours gleaning."

[8] The log of the Daily Southern Cross, 19 September 1863, reported on page 2 that a memorandum, enclosed in a bottle, was picked up by Captain Harris, of Caroline, which arrived in Hobson's Bay during Wednesday night, with a cargo of guano from Cato Island, and was found on the Cato Bank:- "25 June 1863 – Prince Edward, of Auckland, Geo.

[10] A memorial plaque on the north eastern tip of Cato Island commemorates this historic event and reads: "On the 14th day of June 2004, at this highest point in the Coral Sea, Emperor Dale Parker Anderson raised the gay rainbow flag and claimed the islands of the Coral Sea in his name as homeland for the gay and lesbian peoples of the world.

[10] The declaration began, "Homosexual people have honestly endeavoured everywhere to merge ourselves in the social life of surrounding communities and to be treated equally.

[10] The activists founded a camp site on Cato Island which they named "Heaven" after the famous gay nightclub in London as the claimed capital, and "I Am What I Am" was set as the Kingdom's national anthem.

[11] The leader of the protesters, Dale Parker Anderson, was elected Administrator of the territory and then "declared emperor" of the kingdom upon its independence.

However, swimming, reef walking, lagoon snorkelling, bird-watching, seashell-collecting, and shipwreck-exploring were all gay government-sanctioned non-economic activities.

[12] After Australia put marriage equality in to law, the Gay and Lesbian Kingdom formally dissolved on November 17, 2017.

[14] Thomas King, a barque of 346 tons, built for the West Indian sugar run, was taken to Australia for the gold rush.