The greatest influx of people began after Reverend Lake formed the National Park Amusement Company to build an amusement center at the top of Beach Hill, summer cottages along the beachfront, and a 300-foot pier at the foot of Beach Hill. Reverend Lake also formed the National Park Naviga­tion Company to provide steamboat transportation between the Arch Street Pier in Philadelphia and National Park. This Philadelphia/Na­tional Park linkage not only provided large crowds for such beach activities as swimming, boating and fishing, it also radically changed the religious profile of the community. A large portion of the Philadelphia traffic consisted of Irish Catholics that came to National Park to enjoy the resort aspects rather than the religious aspects of the community. National Park changed from an exclusively Methodist Episcopal community to one that was shared about equally with the Catholics.

Up through the 1920's, the Delaware was clear and beautiful and the National Park waterfront offered 1700 feet of white sandy beach. Shad fishing and crabbing were excellent and 69 beachfront cot­tages were available through the summer season. However, in spite of this, resort activity began to decline. Advances in transportation technology began to provide leisure time alterna­tives far more attractive than National Park. The New Jersey seashore offered more activity with more conveniences. As an example, the National Park cottages had no internal plumbing, fire protection, or road access. In fact, most of the cottages had been destroyed by fire by the end of the 1940's, because the cottages were so close together that a fire in one cottage quickly spread to others.

It was in the 1940's that National Park completed its transition from a resort to a rural community. World War II created massive job opportunities in the nearby shipbuilding industries. This caused many summer cottages to be converted for year round usage and brought about an increase in the number of permanent residents. That increase, in turn, created demand for more borough services and greater attention to borough politics. By 1945, National Park had come into its own as a Gloucester County commu­nity.

The 1905 New Jersey State census recorded 160 residents in National Park. Since then it has grown to 1977 in 1940, to 3730 in 1970 to 3205 in 2000.