The Association was successful in its efforts to encourage the United States Government to construct the seawall which was built by Col. Samuel H. Yonge in 1900-1901 to halt bank erosion by the James River along the Association grounds. Colonel Yonge became a serious student of Jamestown history and wrote _The Site of Old “James Towne,” 1607-1698_, a work still available through purchase from the Association. In 1907, the Association made available the grounds on which the Tercentenary Monument was erected, and again in 1956 it provided land on which to place the Jamestown Visitor Center. In 1940 the Association entered into agreement with the United States of America, through the Secretary of the Interior, to provide for a unified program of development and administration for the island. It was at this time that the APVA grounds were designated as Jamestown National Historic Site. The joint cooperative agreement continues in force and the Association and the National Park Service are working together to preserve, maintain, and interpret this historic area. In 1956 it became possible to present the townsite as a single unit when the ferry to the island and the State highway crossing the island were moved upriver above Jamestown. The APVA and the Service then combined their separate museum exhibits to form the displays now seen in the Visitor Center, and consolidated other operations at the center where both are hosts to Jamestown visitors. [Illustration: _Early ceramic types found in the excavations._] _Colonial National Historical Park_ In 1930, by Presidential proclamation, all of Jamestown Island’s 1,559.5 acres (equally divided between marsh and dry land) were included within the boundaries of Colonial National Monument. The monument designation was changed to that of a national historical park by act of Congress in 1936. Actual Federal ownership of the island (other than the 22-acre Association tract) was obtained in 1934, and some years later, a bit of the mainland opposite the western tip of Jamestown was added because of its close ties to the site. Colonial National Historical Park is made up of several areas of which Jamestown is one. It includes, as well, the Cape Henry Memorial, at the mouth of the Chesapeake Bay, where the first settlers who established Jamestown first stopped in Virginia; the Yorktown Battlefield; and the Colonial Parkway. _Colonial Parkway_ This 23-mile scenic motor road connects historic Jamestown, Williamsburg, and Yorktown. Along its course are descriptive markers that give bits of history which often show the interrelation of Jamestown (where the Nation began), Williamsburg (the 18th-century capital of Virginia where important elements of our Revolutionary leadership were nourished), and Yorktown (where the climatic battle in our struggle for independence was fought). _The Study of Jamestown_