Complex sentence: At the beginning of the 19th century, Plymouth's primary industry was agriculture, and its residents the descendants of the Connecticut Yankees who firs settled the town, and thus its architecture resembled that of a small New England village.
Split into simpler sentences: At the beginning of the 19th century, Plymouth's primary industry was agriculture, and many of its residents were the descendants of the Connecticut Yankees who first settled the town. Its early architecture resembled that of a small New England village.