Cadet title created in 1610 when the 6th Tuʻi Haʻatakalaua, Moʻungātonga, installed his son Ngata as governor of Hihifo district, Tongatapu — the third tier of Tonga's tripartite dual-kingship system (sacred Tuʻi Tonga, secular Tuʻi Haʻatakalaua, and now this new administrative line). Over the 17th–18th centuries the Kanokupolu line eclipsed both older titles in real political and military power, and by the 19th century held effective rule over Tongatapu and beyond.
The 19th Tuʻi Kanokupolu, Tāufaʻāhau, was baptized and in 1845 became paramount ruler as King George Tupou I, uniting the Kanokupolu chieftainship with control of the whole archipelago; in 1875, with missionary Shirley Baker's help, he promulgated Tonga's constitution and declared a constitutional monarchy, formally superseding the old title-based polity with the modern Kingdom of Tonga (canonical record 'tonga', start_year 1875) — the House of Tupou descends directly from this line, so continuity runs unbroken into the present monarchy rather than being extinguished.
The atlas holds 3 border frames for Tuʻi Kanokupolu — the shape you scrub through changes in 1610 · 1800 · 1866.
A short monograph specifically on the Tuʻi Tonga / Tuʻi Haʻatakalaua / Tuʻi Kanokupolu tripartite kingship system — the closest thing to a polity-specific source for this exact title. Verified via Open Library (search: 'Classical Tongan kingship' Campbell; edition OL1140650M, ʻAtenisi University, Nukuʻalofa, 1989; no ISBN on record for this small pamphlet edition).
Broad-survey fallback that covers the Kanokupolu line's rise and its 1845/1875 transformation into the modern monarchy in more narrative depth than the short 1989 pamphlet; the same book already used for the sibling Tuʻi Haʻatakalaua record and the modern Tonga record, so this keeps the three-title succession's reading list consistent.