Complex sentence: In 1965 Spruce Knob-Seneca Rocks National Recreation Area became the first NRA under the administration of the U.S. Forest Service and, in 1972 Congress created Gateway National Recreation Area under the management of the National Park Service thereby becoming the first "urban national park".
Split into simpler sentences: In 1965 Spruce Knob-Seneca Rocks National Recreation Area became the first NRA under the administration of the U.S. Forest Service. In 1972 Congress created Gateway National Recreation Area under the management of the National Park Service, thereby becoming the first "urban national park".