In the early 1860s, driven by the threat of war with the United States, British army engineers and local contractors built a coast artillery battery on top of the red-coloured bluffs overlooking the eastern approach to Saint John harbour. It is broadly similar to earlier coastal batteries that still exist at Halifax and Quebec City, but on a more massive scale because artillery was rapidly increasing in size and power during the 1860s. Other heavy batteries were constructed at other Canadian ports during that decade, but all were subsequently rebuilt with more modern structures. Red Head Battery is the only surviving example in the country. It was also the last major defensive work built to guard the strategic overland road from Saint John to the Canadian interior, which was the only means of access from the Atlantic to the interior in winter.