The earliest reference to these parrots was in 1583 in Florida reported by Sir George Peckham in A True Report of the Late Discoveries of the Newfound Lands of expeditions conducted by English explorer Sir Humphrey Gilbert, who notes that explorers in North America "doe testifie that they have found in those countryes; ... parrots".

They were first scientifically described in English naturalist Mark Catesby's two-volume Natural History of Carolina, Florida and the Bahama Islands published in London in 1731 and 1743.

Carolina parakeets were probably poisonous – French-American naturalist and painter John J. Audubon noted that cats apparently died from eating them, and they are known to have eaten the toxic seeds of cockleburs.

The binomial Psittacus carolinensis was assigned by Swedish zoologist Carl Linnaeus in the 10th edition of Systema Naturae published in 1758.

The species was given its own genus, Conuropsis, by Italian zoologist and ornithologist Tommaso Salvadori in 1891 in his Catalogue of the Birds in the British Museum, volume 20.

It was found from southern New York and Wisconsin to Kentucky, Tennessee, and the Gulf of Mexico, from the Atlantic Seaboard to as far west as eastern Colorado.

[Note 5] Its habitats were old-growth wetland forests along rivers and in swamps, especially in the Mississippi-Missouri drainage basin with large hollow trees including cypress and sycamore to use as roosting and nesting sites.

[27] It mostly ate the seeds of forest trees and shrubs, including those of cypress, hackberry, beech, sycamore, elm, pine, maple, oak, and other plants such as thistles and sandspurs (Cenchrus species).

It ate fruits, including apples, grapes, and figs (often from orchards by the time of its decline), and flower buds, and occasionally, insects.

[23][28] It was especially noted for its predilection for cockleburs (Xanthium strumarium),[12] a plant which contains a toxic glucoside,[29] and it was considered to be an agricultural pest of grain crops.

[31] There are no scientific studies or surveys of this bird by American naturalists; most information about it is from anecdotal accounts and museum specimens, so details of its prevalence and decline are unverified or speculative.

The last known wild specimen was killed in Okeechobee County, Florida, in 1904, and the last captive bird died at the Cincinnati Zoo on February 21, 1918.

However two sets of eggs purportedly taken from active nests in 1927 are in the collection of the Florida Museum of Natural History, and genetic testing could prove the species was still breeding at that time.

Hunting played a significant role, both for decorative use of their colorful feathers, for example, adornment of women's hats, and for reduction of crop predation.

Minor roles were played by capture for the pet trade and, as noted in Pacific Standard, by the introduction for crop pollination of European honeybees that competed for nest sites.

Vigorous flocks with many juveniles and reproducing pairs were noted as late as 1896, and the birds were long-lived in captivity, but they had virtually disappeared by 1904.

The modern poultry scourge Newcastle disease was not detected until 1926 in Indonesia, and only a subacute form of it was reported in the United States in 1938.

As well, genetic research on samples did not show any significant presence of bird viruses (though this does not solely rule out disease).