The eastern Delta city-states — Bonny (Ibani), Kalabari (New Calabar), Okrika (Wakirike), Nembe (Brass) and after 1869 Opobo — emerged as Ijo-speaking fishing and salt-making villages on the brackish creeks of the Niger Delta from the 15th century. Portuguese, Dutch and English ships called at them from the 16th century to purchase slaves, and by the 18th century they had become the principal trans-Atlantic slave-exporting ports of the Bight of Biafra, eclipsing even Whydah and Lagos in volume during peak years.
The distinctive institution of the Delta city-states was the 'house' (wari) — a multi-ethnic, commercially organised corporation headed by a senior trader and built up from his family, his trading partners, his canoe crews and the slaves he had acquired and assimilated. The house was a trading firm, a fighting force (canoe houses could field war canoes with cannon), a religious congregation, and a unit of political representation in the Amanyanabo's (king's) council. Houses competed and merged; ambitious slaves could rise to head their own houses. By the early 19th century the king of Bonny was selected from among the heads of houses by a kind of plutocratic election.
King Jaja of Opobo (Jubo Jubogha, c.1821–1891) is the classic exemplar. Sold into the Anna Pepple house at Bonny as a boy from Igboland, he rose to head the house by the 1860s. After losing a war against the rival Manilla Pepple house in 1869, he led his followers out of Bonny and founded a new kingdom at Opobo, on the strategic mouth of the Imo River. He cut Bonny off from the palm-oil hinterland, established direct trade with the Liverpool firm of Alexander Miller Brother & Co. (one of Goldie's founding firms in the Royal Niger Company), and within a decade had made Opobo the dominant palm-oil port of the eastern Delta. Jaja's move was, at base, a monetary strategy: he built Opobo precisely to escape the cowrie- and manilla-rigged Bonny market and to trade palm-oil directly for sterling with Liverpool firms — the one currency the British were not actively crashing. See How the currency fell before the flag.
The Berlin Conference of 1884–85 and the establishment of the Oil Rivers Protectorate (1885, renamed Niger Coast Protectorate 1893) made Jaja's middleman position untenable. Acting Consul Harry Johnston invited Jaja to a conference on board HMS Goshawk at Opobo on 19 September 1887 under a flag of safe conduct, then arrested him, transported him to Accra for trial on charges of obstructing trade, and deported him to St Vincent in the West Indies. He was permitted to return in 1891 but died on the journey at Tenerife on 7 July 1891. His body was returned and buried at Opobo. The kingdom continued under his successors and is today recognised as a first-class chiefdom under the Government of Rivers and Akwa Ibom States. The Amanyanabo of Opobo (currently HRM Dandeson Douglas Jaja) is a direct descendant.