On 11 March 2013 its borders were modified and it was expanded with the incorporation of part of the abolished Municipio XVII.

[1] Since then all the rioni of Rome, which are the city's historic districts, form part of Municipio I together with the localities Delle Vittorie and Eroi.

Municipio I is divided into 11 localities: Since 2013 the territory includes all 22 rioni: R.I Monti, R.II Trevi, R.III Colonna, R.IV Campo Marzio, R.V Ponte, R.VI Parione, R.VII Regola, R.VIII Sant'Eustachio, R.IX Pigna, R.X Campitelli, R.XI Sant'Angelo, R.XII Ripa, R.XIII Trastevere, R.XIV Borgo, R.XV Esquilino, R.XVI Ludovisi, R.XVII Sallustiano, R.XVIII Castro Pretorio, R.XIX Celio, R.XX Testaccio, R.XXI San Saba and R.XXII Prati.

Last election occurred on 3 and 17 October 2021: The table below shows the current composition of the council: Here is a list of presidents of the municipio since the office was created in 2001: The area of the municipality occupies the central districts of the town, including the whole historic district enclosed by the Aurelian Walls and the Janiculum walls and crossed by the Tiber, which makes part of UNESCO's List of World Heritage Sites.

The ancient core of the municipality is the historic seven hills (Palatine, Aventine, Capitolium, Quirinal, Viminal, Esquiline and Caelian), as well as the Janiculum, the Pincian Hill and the artificial hillocks of Monte Testaccio and Monte Giordano.