Short answers, pulled from the story.
Roman Emperor Antoninus Pius issued a directive in 142 AD to build a new frontier across the Central Belt of Scotland. Quintus Lollius Urbicus, governor of Roman Britain at the time, supervised the initial effort.
The structure was built using turf on top of stone foundations rather than solid rock like its southern counterpart. A deep ditch protected the northern side while a military way ran along the south.
Nineteen forts stretched across the Central Belt from Old Kilpatrick on the Firth of Clyde to Carriden near Bo'ness. Smaller fortlets filled gaps between major strongpoints, creating a dense network of control.
Roman legions withdrew from the Antonine Wall by 162 AD just eight years after completion. Attacks from Caledonian tribes made holding this northern position increasingly difficult over time.
Bede wrote in 730 that Britons built the turf wall rather than Romans, confusing its origins entirely. Medieval chroniclers called it Gryme's Dyke linking the name to imaginary kings or even the devil himself.
The site became an extension to Frontiers of the Roman Empire on the 7th of July 2008 according to UNESCO records. Historic Environment Scotland now manages several individual sites including Bar Hill Fort and Bearsden Bath House.