For most of the county’s history, I think most of the population lived in the eastern part of the county. Now, the 3 most populous municipalities, Derry, Salem, and Londonderry, are all in the western part of the county. The population grew in the western part of the county after I-93 was built. So I think the county seat was moved closer to the center of population of the county.
I heard the building in Exeter needed lots of repairs and was too small for the court. I believe land was donated in Brentwood that sweetened the deal.
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