During the earlier Roman period it was common for wealthy landowners to construct unfortified villas on their lands.
After the fall of Rome, increased social instability and military conflict necessitated more austere, defensible types of structures.
In the United States, historically a fortified house was often called a fort or station depending on the region.
While some fortified houses were sometimes used by militias, state and federal military units, their primary purpose was for private or civilian defense.
[1] Examples of historic private or civilian fortified houses built include;