Antoninus Pius was the fourth of the so-called Five Good Emperors who ruled Rome in the 1st and 2nd Centuries. His reign was known for its relative peace and prosperity. He was known especially in Britain for having another wall built there.

He was born on Sept. 19, 86, at Lanuvium, southeast of Rome. His father, Aurelius Fulvus had been a consul, as had been his paternal grandfather. The boy spent much of his youth with his grandparents, on a large estate at Lorium. He would later build an imperial palace on land he inherited.

The young Antoninus worked his way up the cursus honorum, serving as quaestor and then praetor and then becoming consul in 120, along with Catilius Severus. He served as proconsul of Asia for a time and then was an advisor to the emperor Hadrian. The emperor adopted Antoninus as his heir on Feb. 25, 138; Antoninus, in turn, adopted Marcus Aurelius and Lucius Verus. These arrangements were part of Hadrian's desire to see an orderly succession to his reign as emperor.

Hadrian died later that year, and Antoninus took the throne. One of his first acts was to deify Hadrian, as was the custom. Antoninus was active in promoting this deification and built several monuments to his predecessor; for this, the Senate added "Pius" to Antoninus's name.

He finished several construction projects begun by Hadrian and had built a mausoleum for the departed emperor and a temple to him. Antoninus also ordered the repair of several prominent structures, including the Colosseum, the Antium aqueduct, and the Ostia baths. New roads drove more trade and commerce throughout the Empire, which enjoyed renewed prosperity, also thanks to Antoninus's fiscal discipline.

One of his major projects of new construction was a northern version of Hadrian's Wall in Britain. The Antonine Wall, begun in 142, was 99 miles north of Hadrian's Wall. This new wall was 40 Roman miles long, or nearly 43 miles long, and ran from the Firth of Forth to the River Clyde. Nearly two dozen forts were built as well.

This new wall was made of hardened turf, with a bit of a stone foundation, and was a bit more than 310 feet high and 16 feet high wide. A deep ditch on the northern side was designed to at least slow down any sudden attacks. On the south side was a road known as the Military Way, which linked all of the forts.

Rome would have occupied all of the territory in between; but although Antoninus succeeded in that regard, he didn't do any better than Hadrian had at conquering the northern tribes. Roman soldiers occupied the Antonine Wall for only eight years.

As was common for most emperors, Antoninus faced warfare during his time on the throne, although none of it was of his making. He didn't participate directly but did oversee wars in Britain, Dacia, Germany, and the Middle East. Rebellions in Armenia, Egypt, Greece, and Palestine occurred on his watch.

Antoninus had married Annia Galeria Faustina; they had four children, three of whom (including both sons) died in infancy. Faustina, his wife, died in 141. In her memory, he had a temple built in her name and also founded the Faustinian Girls, an order for the poor.

He died of a fever, on March 7, 161, at his villa in Lorium; he was 74. As he wished, Lucius Verus and Marcus Aurelius succeeded him peacefully.