Niue became a British protectorate in 1900 at the request of the reigning patu-iki (king), succeeding the informal Niuean monarchy already in the atlas as 'kingdom-of-niue' (which that record's own fate text ends at 1900). Annexed to New Zealand on 11 June 1901 (the same proclamation that annexed the Cook Islands) and administered thereafter as a New Zealand territory via a Resident Commissioner, with the patu-iki title continuing in a reduced customary role.
Achieved self-government in free association with New Zealand on 19 October 1974 under the Niue Constitution Act 1974, becoming the polity already in the atlas as the modern 'Niue' record (Wikidata Q34020), which the atlas dates from 1974.
Open Library-verified (ISBN 9780824855864); the standard modern history of Niue, and its own title's date range (1774-1974) maps almost exactly onto this record's 1900-1974 span -- already cited in the atlas's 'kingdom-of-niue' record for the preceding era, reused here for continuity of sourcing.