The diocese was created by Pope Pius VII in the bull "Militantis Ecclesiae" of 25 September 1806, at the urging of Queen Maria Luisa, Regent of Tuscany.

[4] The erection was opposed both by the Archdiocese of Pisa and the Canons of San Miniato, who would lose territory, power, and income from the change.

[5] In his bull, Pius VII cites statistics as a factor in his decision to create a new diocese: that there were about 26,000 Catholics, and in the suburbs over 46,000.

A cathedral chapter was instituted, consisting of five dignities (the Provost, the Archpriest, the Archdeacon, the Dean, and the Primicerius) and fourteen Canons.

[6] The new diocese was composed of twenty-eight parishes, including eleven inside the city, four in the suburbs, two in the mountains of Livorno, five in the civil district of Colle-Salvetti, and two in Rosignano.