I'm not entirely sure myself, having the same question, but I did a bit of research. As far as I can tell, it was built from Portland limestone in England, and it was built because New Zealand was unable to bring home their dead from the first world war, and built the monument as a lasting memorial.
The Auckland museum was built to store Maori Artifacts and was built over 150 years ago
Auckland city museum in New Zealand.
Whitehead Memorial Museum was created in 1962.
Nakhchivan Memorial Museum was created in 2000.
Memorial Museum of Astronautics was created in 1981.
Shiki Memorial Museum was created in 1981.
Songgwangmae Memorial Museum was created in 2002.
Mitsui Memorial Museum was created on 2005-10-08.
Captain Cook Memorial Museum was created in 1986.
Yamadera Basho Memorial Museum was created in 1989.
Sakamoto Ryōma Memorial Museum was created in 1991.
Kodansha Noma Memorial Museum was created in 2000.