Complex sentence: The ruggedness of the terrain and more economically viable timber resources which were closer to transporation routes, prevented extensive timber extraction, By 1897 the U.S. Department of the Interior managed Washington Forest Reserve essentially preserved the forestland that would later become the park.
Split into simpler sentences: The ruggedness of the terrain and more economically viable timber resources which were closer to transportation routes, prevented extensive timber extraction. In 1897 the Washington Forest Reserve was set aside, essentially preserving the forestland that would later become the park.