The Wairarapa fault runs along to the west of the district. This fault is one of five major active faults in the Wellington region. The Wairarapa Fault last ruptured in 1855, generating an 8.2 magnitude earthquake.
Masterton is Wairarapa's largest town being home to around 25,557 people. The district is flanked by the Tararua ranges to the west and extends to the east coast just beyond Mataikona. There are three iwi within Masterton; Ngāti Kahungunu, Ngāti Kahungunu ki Wairarapa - Tāmaki Nui ā Rua and Rangitāne.