In the early 1820s Ngāti Toa rangatira Te Rauparaha led Ngāti Toa and their northern Taranaki allies on a migration to the southern North Island, displacing the local people in the Kāpiti region. Various Taranaki hapū and Ngāti Raukawa from Waikato migrated soon after to join them. He established a base on Kāpiti Island, which was ideally located for trading with the many European ships that passed through Cook Strait. As a result of this, Ngāti Toa became prosperous and well-armed with muskets.
Te Rauparaha led successive military campaigns to Te Waipounamu (the South Island), ranging as far south as Banks Peninsula. Ngāti Toa and their allies settled extensively across the top of the South Island.
Te Rauparaha signed the Cook Strait sheet of Te Tiriti at Kāpiti on 14 May. He signed a second time, by signing the Herald sheet just over a month later, off Mana Island on 19 June 1840. He signed in the belief that it would ‘guarantee him and his allies the possession of territories gained by conquest over the previous 18 years’.