Joined at the hip !

March 1942 - July 1943

The US Navy constructed 9km of link roads plus a wharf (Yankee Wharf) at Islington Bay, Rangitoto, and built the Causeway linking the two islands. It was made out of scoria and stone, 141 mtrs long and 5 mtrs wide with a short span of bridging for the tide to run through.

The wharf, roads and causeway where intended as a means to move munitons and materials though to the 50 storage magazines built in and around the south western area of Motutapu (see pic above*) and the large US Navy store at Home Bay (the concrete base of the store is still obvious next to the camp ground toilet block).

These facilities were to service the US Pacific fleet which was planning to use the area between Tiri Tiri Matangi and Rangitoto/Motutapu as a base for operations. The fleet never came and the magazines were never used.
* Looking at the old 1943 aerial photo above, you are still able to discern the outline of the roads from 66 years ago in the current day pic. The 1943 photo is taken from Frank Geoffrey Grattan's 1948 'Official War History of the Public Works Department'. You can view this publication at the Auckland Central City Library, Special Collections.  

Before the Causeway

For the last 600 years, since the final significant eruptions of Rangitoto, the islands have always been very close neighbours merely divided by a shallow tidal creek. When Bishop Samuel Marsden, one of the earliest Europeans to set foot on Rangitoto, tried to sail his whale boat between the islands on 4 Nov 1820 he got stuck fast. His boat had to be rescued and carried out to the Waitemata by a large number of local Maori from Motutapu. Guess the channel must have been wider and deeper back then or else it appeared so to Marsden.

The channel today is only a matter of metres wide. The silting up of Gardners Gap is due to a combination of early European land clearance and the construction of the approaches to the causeway itself

The Causeway was completed in March 1942. Prior to this, the commanding officer of the Ninth Coastal Regiment, responsible for co-ordinating and directing the fire of all the Auckland Coastal batteries (The Fire Commander) was based on the summit of Rangitoto. From time to time he was required to inspect the Motutapu Battery. This same day return trip included a low tide walk across the narrow gap separating the islands

What's so special about the Causeway?

While providing easy communication between the two islands, it is significant in that it joins Auckland 's largest and youngest volcano with a chunk of Gondwanaland. Motutapu is an ancient landform estimated between 165 and 180 million years old. 
In February 2008, the Causeway proved rather special for Andrew and Wendy. They couldn't decide whether to get married on Rangitoto or Motutapu so compromised by taking their vows in the middle of the Causeway bridge.