Lyme Regis is known as "The Pearl of Dorset" for obvious reasons but it could easily have been "The Pearl of Devon".
In the 8th century, the border between Dumnonia (Devon) and Dornsaete (Dorset) followed the Lim down to the sea but today it veers southwestwards away from the Lim as the river enters Lyme to join the coast at Devonshire Head. Why this change, without which Lyme's famous Cobb harbour would be in Devon? The answer is most probably "Salt".
Salt was a valuable commodity in the 8th century and the coast round Lyme was a source. At that time, the seaboard at Lyme was edged with salt marshes and it is believed that a salt extraction industry existed. In 774AD the West Saxon King Cynewulf granted a helmet shaped area of land on the west bank of the Lim at Lyme to the bishopric of Sherborne. Its boundary is the current county boundary so Lyme is in Dorset! This western part of Lyme became known as Lyme Abbas (Abbot's Lyme) with the eastern part known as Lyme Regis (King's Lyme).
You can read what little more we know about salt production in Lyme in our Generalities paper here.
If you would like to know more about the history of the county boundary then contact Katherine Barker of The Dorset County Boundary Survey team who provided the diagram.