The story of their first season in Serie B is chronicled in the book The Miracle of Castel di Sangro by Joe McGinniss.

At the end of the war, a priest named Don Arbete organized a football team to help to rebuild the community.

Their savior came in the form of Pietro Rezza, a southerner from the region of Apulia who had married into one of the town's wealthiest families and who left the operation of the team to his niece's husband, Gabriele Gravina.

Gravina brought in manager Osvaldo Jaconi, who worked a minor miracle by leading the team to a seventh-place finish.

Still, it was mind-boggling that a team from tiny Castel di Sangro deep in the hinterlands of the Abruzzo not only made it there but lasted seven years.

Simply staying in C1 itself would have been quite an accomplishment, but Jaconi outperformed far beyond that; that season they finished second, meaning they qualified for the playoffs to determine promotion to Serie B.

At home, it looked as if the match would end in a scoreless tie (meaning that Castel di Sangro would lose on the aggregate score), when Jaconi made a seemingly bizarre substitution.

As the shootout progressed, neither side missed, until the eighth round, when Spinosa made a seemingly impossible save, securing the victory — and promotion — for his team.

[5] Having been in the lower leagues, the team was forced to upgrade their stadium in accordance with Serie B regulations, and as construction hadn't finished by the beginning of the season, they played their first several home matches in nearby Chieti.

After months of delays, when it finally did open in December, the severe winter weather and poor fertilizer made the pitch unplayable, causing their first fixture there to be called off.

According to McGinniss, the last match of the season was fixed; he overheard players before the match discussing how Bari, who needed a victory to ensure promotion to Serie A, would be allowed to score three goals and win, with Castel di Sangro allowed one consolation goal from a penalty kick.

One player explained to him that Bari had asked for a favor, and even had they not done so, Castel di Sangro was unlikely to win anyway because of the emotional and physical toll consumed by the relegation battle.

In 2006–07, Pro Castel di Sangro clearly won the league with an 11-point advantage to the second-placed team,[10] moving up the ranks of Italian football to Eccellenza for the next season, with a squad featuring former Serie B protagonists Bonomi and Martino.

Pro Castel di Sangro then ended their first Eccellenza campaign of the 2000s with a mid-table placement, in a league which also featured former professional teams Chieti (who were eventually crowned champions) and L'Aquila.