During the seventeenth century plantation of Donegal, Captain Crawford received a grant of 1,000 acres in this area, where Sir George Merbury established what would become Letterkenny town. According to historical records from the period, Merbury created a market town of 50 thatched houses, thirteen of which boasted more substantial clay and stone walls, along with a watermill. The settlement centred around a fortified bawn; a defensive structure typical of plantation architecture; which contained a large stone dwelling house and featured four flanker towers for protection.

By 1654, the Civil Survey of Donegal painted a picture of a thriving plantation town, complete with a Friday market, two annual fairs, a church, and a bridge crossing the River Swolly. The bawn and its associated castle appear to have stood near the present site of Conwal Church of Ireland church, with Castle Street originally running south from the church directly to the castle grounds. This fortified complex likely occupied the area near the southern angle of Mount Southwell, a location that remained significant enough to leave its mark on local place names well into the modern era.

Today, ghostly traces of this plantation settlement persist in Letterkenny’s urban landscape. The names Castle Gardens and Fort Well, marked on Ordnance Survey maps, preserve the memory of where the seventeenth century house and bawn once stood. A large two storey house now occupies what may have been the original castle site, surrounded by substantial stone walls that could potentially incorporate remnants of the plantation fortifications. These surviving place names and possible structural elements offer tantalising glimpses into Letterkenny’s transformation from a modest plantation outpost of thatched houses into the bustling Donegal town it is today.