Complex sentence: Much of the old growth forest in this region was destroyed by logging in the early part of the 20th century; some of the trees that grow there today were planted by the Civilian Conservation Corps in the 1930s.
Split into simpler sentences: Much of the old growth forest in this region was destroyed by logging in the early part of the 20th century. Some of the trees that grow there today were planted by the Civilian Conservation Corps in the 1930s.