Itsekiri kingdom of the western Niger Delta founded c. 1480 by Prince Ginuwa, son of the Oba of Benin; its Olu (king) became Christian in 1570 under Portuguese missionary influence, and the kingdom served as a commercial and cultural bridge between the Benin hinterland and Atlantic trade through the 16th-19th centuries.
Warri's chiefs signed a British protectorate treaty aboard HMS Flirt in 1884; after the Itsekiri merchant-ruler Nana Olomu was defeated by the Royal Navy in 1894 the kingdom's autonomy effectively ended, and in 1900 it was fully incorporated into the Southern Nigeria Protectorate under a British-appointed paramount chief. The Olu-ship survives today as a non-sovereign traditional monarchy within Delta State, Nigeria (the current Olu, Ogiame Atuwase III, was crowned in 2021).
The atlas holds 3 border frames for Kingdom of Warri (Iwere) — the shape you scrub through changes in 1480 · 1515 · 1765.
Polity-specific history of the Warri (Iwere) kingdom and its Olu dynasty, published in Sapele, Nigeria; Open Library edition gives an uncertain 1980s publish date (LC record dates the edition 1980).