Many remains found on the town indicate that gallic tribes lived in this locality race before the Roman presence. All that remains of this period that the traces of an ancient dolmen Dennemont.
Followed the Roman legions and settle it in tilling a field as the remains of a limestone burial slabs were discovered Dennemont.
Follainville had to suffer the invasion of Normandy. In 1087, when William the Conqueror vowed to destroy the town of Mantes, he sent Ascelin Goël destroy the crops and vineyards. The latter ordered the Norman troops to cut the trees nearby.
Castle Dennemont, now destroyed, belonged to the philosopher Condorcet from 1785 to 1793 and Mr. Roissy, sub-prefect from 1823 to 1833. There are still some boves next to the current nursing home, traces of the ancient castle, one of which retains a press to apple wood screws.
The stronghold until 1792 depended Dennemont St Martin-la-Garenne.
