Complex sentence: Once part of Carthage, this area was set off in the mid 19th century and subsequently organized into two plantations (Perkins and Washington), both of which had dissolved and reverted to unorganized townships by the early 20th century.
Split into simpler sentences: Once part of Carthage, this area was set off in the mid 19th century and subsequently organized into two plantations (Perkins and Washington). Both had dissolved and reverted to unorganized townships by the early 20th century.