Complex sentence: The town supplied many of the whalers used on the East Coast in the first half of the nineteenth century, the last one, the "Wanderer," being built in 1878, shortly after the discovery of oil in Pennsylvania.
Split into simpler sentences: The town supplied many of the whalers used on the East Coast in the first half of the nineteenth century. The last one, the "Wanderer," was built in 1878, shortly after the discovery of oil in Pennsylvania.