Crownhill was originally known as Knackersknowle, meaning "the hill of the knacker's yard". One variation is Knockers Hole. In 1860 a fort was built on a high piece of land, just to the north west of the village, on the site of a building called Crown Hill, presumably because of its dominating position overlooking all the surrounding area. The village and surrounding area eventually adopted the same name. The fort was one of many Palmerston forts built around Plymouth under the instruction of the then Prime Minister, Lord Palmerston, as a defence for the dockyard at Devonport against the French. The construction of these forts was eventually found to be unnecessary and as such they have been called "Palmerston's Follies". Crownhill Fort has now been restored as a tourist attraction and its guns are fired more often now then they ever were in anger.
Most people hardly notice CrownhillFort as they go past, it is so well hidden from the outside world, and that was exactly the intention when it was built in the 1860s.
CrownhillFort has great importance today, as the last of this country's true castles and the most important of the great Victorian forts built to defend Plymouth from attack by land as well as sea..
In particular, Crownhill boasts the only working Moncrieff Disappearing Gun in the world, now standing on the northeast rampart, a fitting monument to the ingenuity of the Victorian military engineers.