Having discharged the offices of quaestor and praetor, and twice served as consul, Antoninus was appointed by the emperor Hadrian as one of the four ex-consuls to administer Italy, then greatly increased his reputation by his conduct as proconsul of Asia. He acquired much favor with the emperor Hadrian, who adopted him as his son and successor February 25, 138, after the death of his first adopted son Aelius Verus, on the condition that he would adopt Marcus Annius Verus, the son of his wife's brother, and Lucius, son of Aelius Verus, who afterward became the emperors Marcus Aurelius and Lucius Aelius Verus.
Antoninus in many ways was the ideal of the landed gentleman praised not only by ancient Romans like Varro and Cato the Elder, but later scholars of classical history, such as Edward Gibbon or the author of the article on Antoninus Pius in the ninth edition of the Encyclopedia Britannica:
One of his first acts as Emperor was to persuade the senate to grant divine honors to Hadrian, which they had at first refused; his efforts to persuade the Senate to grant these honors is one of the reasons given for his title of Pius (dutiful in affection; compare pietas). Two other reasons for this title are that he would support his aged father-in-law with his hand at Senate meetings, and that he had saved from death those men that Hadrian, during his period of ill-health, had condemned to death. He built temples, theatres, and mausoleums, promoted the arts and sciences, and bestowed honors and salaries upon the teachers of rhetoric and philosophy.
There were several military disturbances throughout the Empire in his time, in Mauretania, Judea, and amongst the Brigantes in Britain, but none of them are considered serious. The unrest in Britain is believed to have led to the construction of the wall of Antoninus from the Firth of Forth to the Firth of Clyde.
By his wife Faustina he had two sons and two daughters, but all died before his elevation to the throne -- except Annia Faustina, who became the wife of Marcus Aurelius. On her death in the third year of his reign, he honored her memory by the foundation of a charity for orphan girls, following the practice of prior emperors in endowing an Alimentaria to promote the welfare of children and an increased population.
Antoninus died of fever at Lorium in Etruria, about 12 miles from Rome, on March 7, 161, giving the keynote to his life in the last word that he uttered when the tribune of the night-watch came to ask the password -- "Equanimity"
The only account of his life handed down to us is one of the Scriptores Historiae Augustae.
He was also the first Roman emperor to appear in Chinese historical sources.
Hadrian (117 - 138)
Marcus Aurelius (161 - 180),
Lucius Verus (161 - 169)