[Detail from "The Descent from the Cross" by Pedro Machuca, which hangs in the Prado Museum. The Prado's online gallery displays the full painting with interesting commentary. The painting's frame includes an inscription that says, "This altarpiece was ordered made by do a Inés del Castillo, wife of Garcí Rodríguez de Montalvo, alderman of this town." The man in the armor is apparently Garcí Rodríguez de Montalvo, though he may be the author of Amadís or his nephew or grandson, who had the same name.]
In about 1450 in the city of Medina del Campo, Garcí Rodríguez de Montalvo was born into the politically connected Pollino family, which held a hereditary seat on the city council. Medina del Campo, in the plains of central Castilla y León near Valladolid, enjoyed a large population and great wealth and from its two huge sheep fairs; wool held enormous economic importance at the time.
As a member of the minor nobility, Rodríguez de Montalvo grew up enjoying falconry and dreaming of great feats of arms, according to what he wrote about himself in the novel Las Sergas de Esplandián.
He had several children and earned his living as an alderman, verseeing municipal administration. The nobility also provided men at arms, and he joined the military regiment of Medina del Campo in the initial campaigns in the War of Granada. He was named a knight by the King Fernando and Queen Isabel in 1482 for his defense of Alama.
Although scholars debate the exact dates, he probably worked on Amadís de Gaula between 1482 and 1492, "correcting and polishing" medieval Books I, II, and III, adding Book IV (by changing the ending of Book III), and creating a fifth book about Amadis's son, Las Sergas de Esplandián (The Exploits of Espandian). Book I remains closest to the original. In some later editions, his name is inexplicably given as Garci Ordó ez de Montalvo.
In 1497 he (or his grandson or nephew of the same name) and another man from Medina del Campo were sued for adultery and sentenced to two months of exile from the province of Valladolid. In 1502, he was witness to a wedding — a secret one in Coca Castle between María de Fonseca and the Marqués del Cenete, Rodrigo de Mendoza; secret weddings were illegal at the time, but nothing involving the powerful Fonseca and Mendoza families could stay secret long.
These notes in legal documents are the only proof he was alive and doing anything.
He probably died in 1505, although that's far from certain. He may or may not have seen Amadís de Gaula achieve publication, since the date of its initial publication is also not completely certain.
In all, we don't know much about him or his life, and if he hadn't taken it upon himself to "bring together the writings of light things of little substance" so that "some shadow of remembrance remain of me" (as he wrote in the prologue to Books I to III), Garci Rodríguez de Montalvo would have been a forgotten footnote in history.
Ars longa, vita brevis.