Caligula’s real name was Gaius Julius Caesar Augustus Germanicus (after his ancestors Julius Caesar and Augustus). But everyone called him Caligula because when he was a little boy he lived in military camps where his father was the general. In the camps, he wore little soldier boots. So the soldiers called him “Little Boots”, which is Caligula in Latin.
Caligula’s father, Germanicus, was Augustus’ adopted grandson, and Caligula’s mother, Agrippina the Elder, was Augustus’ granddaughter. Caligula was born on August 31st, 12 AD. He had four brothers and three sisters. Two of Caligula’s brothers died before they grew up. Caligula’s father also died when Caligula was only seven. It’s possible that the emperor Tiberius poisoned Caligula’s father to get him out of the way. After his father died, Caligula’s mother Agrippina got into a long fight with Tiberius about whether he had really poisoned him.
Because of this fight, Tiberius seems to have wanted to get Caligula more under his control. In 27 AD, when Caligula was fifteen years old, he and his three sisters went to live with their great-grandmother Livia, who was Tiberius’ mother. Imagine how you would feel living with the mother of the man who poisoned your father! The kids stayed there for two years, until Caligula was seventeen.
Then Tiberius ended his argument with Agrippina by arresting her and keeping her prisoner on an island, where the guards beat her and abused her. Tiberius also killed Caligula’s two older brothers. Caligula’s brother Nero either was murdered or killed himself. Caligula’s other brother, Drusus, was locked in a dungeon and starved to death – at the end, he tried to eat the stuffing of his mattress because he was so hungry.
After all this, Caligula and his sisters went to live with their mother’s mother Antonia. During this whole time, the teenagers were pretty much prisoners, and had only each other for friends. Suetonius and other Roman historians say that Caligula and his sister Drusilla were more like boyfriend and girlfriend, but we don’t know that for sure.
After two more years, in 31 AD, Tiberius made Caligula come live with him on the island of Capri. At this time Caligula was nineteen years old. Suetonius writes about this time as if all the two guys ever did was party, drink, and hang out with pretty girls and good-looking boys, but he might be wrong about this. Caligula seems to have been very good at keeping on Tiberius’ good side, unlike his other relatives. By 33 AD, his mother Agrippina starved herself to death (or maybe was starved to death).
Tiberius died in 37 AD, when Caligula was 25 years old. In his will, Tiberius left control of the Roman Empire jointly to Caligula and to Tiberius’ grandson, Tiberius Gemellus, but Caligula seized all the power for himself anyway. In the beginning everybody loved Caligula. Priests sacrificed hundreds of cows and sheep and pigs in his honor.
But by 39 AD it was clear that Caligula suffered from a mental illness, which may have been a rare illness called Wilson’s Disease, and this made him act weirder and weirder. He seems to have begun to think of himself as a god. Caligula’s mental illness took over his life more and more as he got older. Suetonius says Caligula made his horse a priest, ordered the sunto rise in the middle of the night, and forced senators to run alongside his chariot.
By the time he was 29 years old, Caligula was so disabled that the people near him thought it was just impossible for him to rule anymore. But there wasn’t any way to stop being Emperor except to die, because the Senate had voted Caligula’s powers to him for life. So in 41 AD some of Caligula’s guards stabbed him to death, and made his uncle Claudius emperor instead.
Classical Rome, by John Clare (1993). For kids, the whole political history from beginning to end.
Oxford First Ancient History, by Roy Burrell (reissued 1997). Easy reading. It skips around a lot, not trying to tell everything, just highlights.
The Romans: From Village to Empire, by Mary Boatwright, Daniel Gargola, and Richard Talbert (2004). Okay, it’s a little dry, but it is up to date and has all the facts you could want.
The Roman Revolution, by Ronald Syme (1960). Still a classic.
From the Gracchi to Nero: A History of Rome from 133 B.C. to A.D. 68
by H. H. Scullard (1959, 5th edition 1990). Another classic.