The municipality of Castelnuovo Magra contains the frazioni (subdivisions, mainly villages and hamlets) Colombiera, Molicciara, Palvotrisia, Molino Del Piano and Vallecchia.

The local dialect (referred to in Italian as Lunigianese or similar names) constitutes a variety of Emilian rather than Ligurian.

After the fall of the Western Roman Empire, it was held by the bishops of Luni; the name of the borough appears for the first time in a document from 1203.

The town was visited by Dante Alighieri on 6 October 1306, to end a long series of conflicts between the bishops of Luni and the Marquis Malaspina and opened a new course in local history.

The artwork was believed stolen in a raid on 13 March 2019, but it was revealed that Italian police, tipped off about the possibility of the planned theft, had replaced the painting with a copy in a sting operation.