In April 1857, at Rangiriri, Potatau agreed to become king. He was crowned and anointed at Ngaruawahia in June 1858.
At his installation, many chiefs of the North Island laid their lands and service at Potatau's feet. Many mountains, the pou (boundaries) of the Rohe Potae (Kingitanga territory), were named as the guardians of the territory under Potatau's dominion. Potatau's subjects hoped to keep the lands and their communities together by removing the temptation of ready money through selling. These lands were to become the 'Crown lands' of the Maori kingdom.
In his speech of acceptance Potatau stressed the spirit of unity symbolised by the kingship, likening his position to the 'eye of the needle through which the white, black and red threads must pass'. He called on his people to 'hold fast to love, to the law, and to faith in God'.
Maori also saw the Kingitanga as a spiritual force carried from marae to marae. Its symbols, such as the king's flags, the pataka (carved storehouses) and runanga (tribal council) houses, the mountains and boundaries, were imbued with tapu (sacredness) and the mana (authority) of the kingdom.
A number of titles were considered for this new position, including 'Father of the Tribes', Ariki Taungaroa (chief of chiefs), Toihau (supreme head) and Rangatira (chief). Critics complained that there was nothing original about the Kingitanga and that it was simply copying the British monarchy. Te Moananui of Hawke's Bay, however, argued that as there were many chiefs, the title king should be used – the position had to be unique and the title needed to set the leader apart from others.
Waikato was rich in resources and was strategically placed in the centre of the island, surrounded by all the most powerful tribes. Any king and his people had to be able to sustain the burden of continuous hospitality on a grand scale, so Waikato's level of resources was key. Potatau himself was a great warrior and in recent times was seen as the protector of the tribes of the Auckland isthmus. His status and mana was not only personal but also derived from his kin connections with many iwi. He had mana in some European circles, enjoying good relations with successive governors. As early as 1841, Governor William Hobson had reported to London that Potatau was the most powerful chief in New Zealand.
In June 1860 King Potatau died at his home in Ngaruawahia and was succeeded by his son Tawhiao. Tawhiao would face many challenges during his reign, in particular war and the subsequent confiscation of land as the Kingitanga clashed head-on with the European government.