The current name of the square was chosen after the plebiscite of 21 October 1860 decreed the annexation of the Kingdom of the Two Sicilies to the Kingdom of Sardinia.

In 1885 a monumental fountain was installed in the center of the square, designed by Federico Travaglini on the occasion of the inauguration of the new Serino aqueduct. At the ceremony of activation of the fountain, which took place on May 10, King Umberto and his wife Margherita participated. The fountain, dismantled in the first half of the following century, returned to the piazza one hundred years after its first installation, in 1985, on the occasion of the centenary of the inauguration of the aqueduct, and this time it was subsequently dismantled.

da Wikipedia