The island consists of one main scoria cone with a deep crater, a small remnant arc of the tuff ring forming the cliffs in the northeast, and the upper portions of lava flows.

[4][3] The history of Motukorea prior to European arrival is not well documented, and while many of the sources available speculate as to the origins of Ngāti Tamaterā mana whenua and their right to sell the island in 1840, few dispute it.

Opinion is divided as to why this may be, Phillips postulates that mana may have been vested in return for assistance in battle,[6] whereas Monin regards the occupation and sale of Motukorea as evidence of more widespread penetration of the inner Gulf by numerous Hauraki iwi and hapu.

The archaeological remains suggest Motukorea was intensively occupied in pre-European times, with people engaged in stone working industry, marine exploitation, gardening of the fertile volcanic soils, and establishing open and defended settlements.

[citation needed] ‘Archaic’ type artifacts found on the island include worked moa bone, and one-piece fishhooks.

[3] Starting from 1820, early European visitors included Richard Cruise, Samuel Marsden and John Butler, who both traded with Maori for produce.

Brown and Campbell settled on the western side of the island from 13 August 1840, making it one of the earliest European settlements in the Auckland area.

[12] They built a raupo whare and ran pigs on the island, using it as a base from which they aspired to establish and supply the town of Auckland as soon as land was available on the isthmus.

[13] Not long after Brown and Campbell had taken up residence on the island, Ngāti Whātua chief Āpihai Te Kawau gifted it to Captain Hobson in order to entice him to select Auckland as the new capital for the colony.

[21][22] Browns Island is also significant in aviation history, with the Barnard brothers of Auckland carrying out what may have been New Zealand's first glider flights from the upper slopes of the cone in June 1909.

Controversy surrounding the proposal forced the plan to be abandoned and the island was eventually purchased by Sir Ernest Davis, who presented it as a gift to the people of Auckland in July 1955.

After the demise of the Hauraki Gulf Maritime Park Board in July 1990, the Auckland City Council was again the designated administering body, and passed back the responsibility for management to the Department of Conservation.

For small craft the best landing is on the more sheltered northern side of the island where there is a 100 m (328 ft) long beach, backed by a steep cliff.

The flatter areas to the west have very large part submerged mussel beds which extend out 100 m (328 ft) from the shore preventing easy landing.