The origins of the Archpriest Church of Saint John the Baptist date back to the 12th century. It was dedicated initially to Saints John the Baptist and George. In 1460, it was elevated to the status of archpriest church, and to this day, the local parish priest holds the honorary title of Archpriest. In 1861, the church was officially recognized as a leading parish church, and the archpriest was granted the privilege of wearing special ceremonial vestments.

The current building stands on the ruins of two earlier churches. The first, dating from the 12th century, was demolished in the 15th century and replaced by a Gothic-style church, which was consecrated in 1471. Only a few elements of that structure survive: a wooden statue of Saint John the Baptist and the altarpiece of the main altar, painted in 1580.

The construction of the present church began on November 3, 1617, and the main structure was completed by 1640. From this period comes the magnificent gilded altar canopy. It features a pyramidal design with three tiers supported by a series of sculpted lions. The façade added several decades later has a horizontal crowning element made of sandstone, including a portal, niches with statues of Saints Peter and Paul, a Palladian-style window, and a decorated pediment.

Inside, the church holds a remarkable collection of sacred art. Among the highlights are an altar by the Manni sculptors; paintings, frescoes and some statues by Ignazio Hillipront, a German sculptor who settled in the Bergamo area. Hillipront also designed the richly carved furnishings of the sacristy in the early 18th century — recently restored to their former splendor. The church also houses a valuable collection of sacred vestments and relics.

Among the side altars, one particularly worth noting is the Altar of Saint Sebastian, the civic patron saint of Casnigo.

The Archpriest Church of Saint John the Baptist stands as a significant example of religious architecture and sacred art, bearing witness to centuries of local history and devotion.