On January 25th, 1873, the foundation stone of the first non-catholic church to be built inside the city walls was laid in Via Nazionale. The date was significant, for January 25th is the Feast Day of the Conversion of St Paul, and the apostle was to be the patron saint of the new church, which would be called St Paul's Within the Walls (San Paolo entro le Mura) to distinguish it from the ancient and much more famous basilica of San Paolo fuori le Mura (St Paul Outside the Wall).
For centuries Rome had been ruled by the popes, who insisted that all non-catholic worship had to take place outside the city walls. But on September 20th, 1870, the papal rule of the city came to an end and Rome became part of the Kingdom of Italy, which had been established in 1861.
The new constitution allowed for freedom of worship and the building of non-catholic churches within the city walls. Rome's American community lost no time in raising funds to buy a plot of land on the newly created via Nazionale. They chose the British architect, George Edmund Street (1824-81), who would go on to design the church of All Saints' for Rome's Anglican community.
St Paul Within the Walls was finally consecrated in 1877.