The move of the capital to Rome in 1871 left Florence seriously indebted and with many unfinished projects. Despite an initial decrease due to the transfer of the state bureaucracy, the population continued to grow even in the most central areas, favouring the process of saturation of the areas within the lots set aside for construction and consequent building. The redevelopment of Mercato Vecchio, which resulted in the expulsion of most of the area’s inhabitants, aggravated the building density of other working-class neighbourhoods, such as Santa Croce and San Frediano.
The industrialisation of the city, which was considerable in the years preceding the First World War, consolidated the neighbourhoods envisaged in the Poggi plan and opened the way for further expansion. The new factories were located patchily, where there happened to be land and infrastructure available. The city’s industrial centre of gravity thus shifted from the Pignone area, outside Porta San Frediano, where the gasworks had existed since the mid-nineteenth century, to the strip north of the city. The railway yards of Campo di Marte, Porta al Prato and, above all, Ponte a Rifredi became poles of attraction for the new factories, consequently orienting the city’s urban development.
The growing demand for social housing caused an urgent need for new neighbourhoods, which sprang up near the new industrial settlements. Their fabric, consisting of basic two-storey terraced houses, still characterises several areas of the city, such as San Jacopino, Rifredi and Ricorboli. The experience of large workers’ blocks of flats, now built by the Istituto autonomo case popolari (autonomous housing institute), also continued: the blocks in Via Rubieri, Via Bronzino, Via Erbosa and Via Circondaria were built from 1909 onwards. In the less suburban neighbourhoods, however, the middle-class opted for terraced houses and multi-storey apartment blocks.
The city council tried to control this rapid development by commissioning engineer Giovanni Bellincioni to draft an expansion plan in 1915, which was approved in 1924. The plan was limited to the laying out of a road network that extended over the flat land around the city, stopping at the foothills and prefiguring the future development of Florence towards the west. According to the plan’s provisions, the new quarters of Romito-Vittoria, Gavinana and Campo di Marte would be built in the years between the wars. Bellincioni also included plans for a new hospital centre at Careggi, under construction from 1912.
The plan did not cover the already built-up areas, some of which, however, underwent modification at a later date. Among the most significant projects were those for the Santa Croce district, where several blocks were demolished in 1936 to decongest the building fabric, creating the Piazza dei Ciompi and some adjacent streets. The demolition programme in San Frediano, already begun at the end of the nineteenth century, was also completed, and which saw, among other things, the creation of Piazza Tasso.
The decades between the two wars also saw several urban replacement projects within the old city centre. One was the construction of the National Library (1911-1935), paid for by the convent of Santa Croce; another the new railway station of Santa Maria Novella (1932-1934), which replaced the Maria Antonia. With the new complex, the square in front of it was also completely reconfigured, and the entire old urban fabric along Via Valfonda was destroyed. There were also some smaller-scale works; the opening up of a series of roads in the less dense areas of the centre – including Via delle Mantellate, Via Rucellai, Via Finiguerra – to allow the last free areas to be built on, or the demolition of small portions of the urban fabric to enhance some monumental buildings, as in the case of the San Lorenzo complex.