Gulf of Morbihan
Plessis-Josso, like all 15th century manors in Brittany, had especially an agricultural function as the head of a "domaine" of 1,500 hectares spread over several parishes and with a population of nearly 500 inhabitants. It had several mills, baker's ovens, a chapel and a small private port in the Gulf of Morbihan. Its role was therefore political, economic and administrative.