Pope Innocent III rallied the bishops of Lombardy and wrote threateningly to both combatants, attempting to force them to make peace.

[4] In 1600, the town (oppidum) of Borgo San Donnino, including a territory with seventeen villages, was under the civil government of Ranuccio I Farnese, Duke of Parma and Piacenza.

They were presided over by a provost (una praepositura), who had to be in Holy Orders, since he held the "cure of souls"; he had an annual income of about 1,300 papal ducats.

[7] In the papal consistory of 8 January 1603 Pope Clement VIII appointed the last provost, Papiro Picedi da Castel Vezzano, to be the first Bishop of Borgo San Donnino.

A brief (breve) addressed to him on the same day informed him of his appointment, recalling that Picedi had been a priest of the diocese of Luni-Sarzana; that he held the degree of Doctor in utroque iure; that he had been a Referendary of the Two Signatures (judge in the Roman Curia); and that he was a familiaris of the Pope.

[9] In 1828, Bishop Aloisio San Vitale was assigned the task and the honor of creating the new diocese of Guastalla by Pope Leo XII.

The diocesan seminary was headed by a priest who was also the Vicar General of the diocese, and it had five professors and two masters; there were thirty-eight students.

On 14 January 2003, the Bishops of Fidenza, Parma, and Piacenza entered into a friendly agreement for the adjustment of their diocesan borders.

[14] The most famous native son of Borgo San Donnino was Cardinal Innocenzo Ciocchi del Monte, the adopted nephew of Pope Julius III.

He ordered the minutes of the meetings published, to which he had appended thirteen enactments of popes or Roman curial offices.

Bishop Vincenzo Manicardi (1879–1886) presided over a diocesan synod on 5–7 June 1883; it was particularly concerned with issues raised by the First Vatican Council.