Who was Offa?
Offa was king of Mercia from 757 to 796 AD. His kingdom covered the area between the Trent/Mersey rivers in the north to the Thames valley.
What is Offa's Dyke?
Offa's Dyke is a linear earthwork which roughly follows Welsh/ English boundary. When it was originally constructed it must have been about 27m wide and 8m from the ditch bottom to the bank top. Why it was built is still a mystery. The dyke appears to be constructed in a response to events that happened in Wales. It is thought construction started around 785 AD and it took several years to build. The earthwork had only a short period of importance and then it was abandoned.
The dyke now
Over time housing and industrial development have damaged and destroyed the dyke -an obvious example is the stretch in Chirk where a railway track was built.