In the 1st century BC Forum Popili become a municipium, and flourished due to its location near the important port of Classis (for which it provided amphorae for wine transport), as well as its own agricultural production.

Their expansion was momentarily halted by the Papal reconquest by Cardinal Gil de Albornoz who, in 1361, ordered the destruction of Forlimpopoli due to its loyalty to the Ordelaffi.

A chronicle from ten years later states that the town no longer existed, the bishopric having been moved to Bertinoro, and the cathedral having been replaced by a fortress, the current Rocca.

Outside the town is the Sanctuary of Santa Maria delle Grazie di Fornò, one of the most notable circular plan churches in Italy (late 15th century).

The basilica of San Rufillo was originally built in the 6th century but it is now a more recent reconstruction; it is home to two canvases by Luca Longhi and Francesco Menzocchi, and the tomb of Brunoro II Zampeschi, lord of Forlimpopoli.