Wind and rain marred a ceremony in 1953 when the Upper Hutt blockhouse was officially made the headquarters for girl guides and boy scouts, who used it until the late 1990s. The blockhouse was the first New Zealand building to be protected by a historic reserve, established in 1916 under the Scenery Preservation Act, after local people lobbied to have it preserved. In 1980 the blockhouse and surrounding land was classified a historic reserve under the Reserves Act 1977 (administered by the Department of Lands and Survey and later the Department of Conservation) but management of it was vested in the New Zealand Historic Places Trust.  

A Historic Places Trust research report notes that the blockhouse had been erected in 1860 when Pākehā settlers feared that conflict between Māori and the Crown over the sale of land at Waitara, Taranaki, would escalate and spread. The timber building, with loopholes for firing through, was surrounded by a defensive earthwork and was occupied until 1861 by a small militia. It is a very rare type of defensive building, and its early preservation is evidence of a growing public concern to retain traces of New Zealand's colonial history.