Until the late 14th century, there are two parish churches in La Ferte: Condetz and Saint-Nicolas.
Saint-Denis was first a small chapel successively enlarged.
The church was built Condetz between the 9th and 10th century, replacing the chapel of St. Martin. It was built by the monks of Reuil that since the time of their foundation, watched the religious interests of the people. It was located 500 to 600 meters from the Saint-Martin, near the Marne.
The church of Saint-Étienne Condetz, located on the other side of the river, was eccentric to the castle. The celebration of the offices are located in often compromised.
In the early 15th century, a movement of population, largely due to the various invasions and the war against the English, drove people to seek help and protection inside the fortress. The people chose as "chapel rescue" the Belfry (or watchtower). It was enlarged gradually at the expense of the parishioners. It is a little later than the last one built bays encompassing the tower. The church of Saint-Denis was built between 1620 and 1625.
According to the journal of Father Duchene, despite its poor condition, the church of Saint-Étienne was still parish office until 1637. Its use is less frequent, they abandoned the idea of repair and damage became irreparable.
In 1750, at a meeting of the city and the parish, which was held at the Town Hall, it was decided that the materials from the demolition of Saint-Étienne serve the restoration of Saint-Denis. According to the oldest church bulletins, in 1580, the church of Saint-Denis had already twice named Saint-Étienne Saint-Denis. Simultaneously serve both churches until 1624. The shape of the tower of the present church dates from its reconstruction in 1750, it had a carillon. The organ was completed October 29, 1628, Marshal de la Force, lord of the city at that time, came to hear the first pipe.