The church Saint-Jean-Baptiste de Jasseron, of remarkable historical depth, is part of the landscape of the Revermont, a transitional territory between Bresse and the first Jurassian reliefs, long perceived as a natural border and a corridor of traffic between Bresse, Franche-Comté and Savoie. The village appears very early in the sources: its parish is attested from the tenth century, given by Richer de Coligny to the Abbey of Condat (Saint-Claude), which founded a priory there. This seniority makes it one of the oldest structured parishes in the Bressan territory and indicates the existence of a place of worship organized long before the village of Bourg-en-Bresse was established. The term Saint John the Baptist, the parish's seniority and topography form a rare cluster of clues in the region, suggesting the existence of a primitive Baptist church.
The exterior features two rare elements: an outdoor desk, formerly linked to public announcements, and an outdoor bentier, carved stone to the right of the gate. This benefactor served for sprinkling, purification rites, blessings and sometimes processions. Its exceptional presence in the region refers to ancient liturgical practices and could bear witness to a high medieval tradition.
In the 13th century, the church preserves a nave with an apparent structure, a vaulted choir in a cradle, an apse in a lauze and, at the base of the bell tower, walled groined openings. The interior, more expressive, offers a warm nave, a harmonious choir, an apse in lauze and antique furniture, including the statue of Saint-Jean-Baptiste (17th century), inscribed MH. Restoration work is planned in 2026. Today, the church is part of the diocese of Belley-Ars and Masses are celebrated according to the calendar of the parish of Saint-Pierre-Chanel in Revermont.
