Complex sentence: Westfield was once part of the Town of Portland and the natural harbor there was known as Portland Harbor; once the Town of Westfield was established formally in 1823, the harbor area became known as Barcelona.
Split into simpler sentences: Westfield was once part of the Town of Portland and the natural harbor there was known as Portland Harbor. When the Town of Westfield was established formally in 1823, the harbor area became known as Barcelona.