This piece is the only one of Michelangelo's large-scale preparatory models for a sculpture to have survived. It represents the design for a statue to be placed in the New Sacristy, where the artist worked from 1521 to 1534, the year in which he departed to Rome, leaving the project uncompleted.
Michelangelo had planned to set up four statues of rivers gods on the floor of the New Sacristy, arranged in two groups of two beneath the tombs of Duke Giuliano and Lorenzo dei Medici. The work for which the River God in Casa Buonarroti is the model was to have been located at the foot of the tomb of Lorenzo dei Medici, on the left. The drawing with the design for its companion on the right is now in the British Museum. A reference to the statues in Antonio Francesco Doni's La terza parte de' Marmi - where in response to the question "What are those wonderful clay models down there?" the Florentine academic declares "They are for two large figures of marble that Michelangelo wanted to make" - allows us to deduce that the two models were still standing on the floor of the chapel around the middle of the century.
It was very rare for Michelangelo to make use of large-scale models for his sculptures. In this case we now that Clement VII, the pope who had commissioned the statues for the new sacristy, had expressly requested life-size models of them, whose execution could be left, at least in part, to others. Yet these personifications of rivers never got beyond the design stage.
The stirring image of the River God in Casa Buonarroti, represented as a semi-incumbent figure, is yet another example of Michelangelo's unflagging interest in ancient statuary. In fact personifications of rivers in classical world always took the form of male figures lying down. There is a record from 1590 of the first restoration of the work, which remained the property of the Accademia del Disegno for centuries. Over the course of time, however, any notion either of the figure's importance or that it was the work of Michelangelo was lost. The credit for its rediscovery and attribution to Michelangelo (1906) must go to the art historian Adolf Gottschewski and the sculptor Adolf von Hildebrand.