The island measured "not above 400 acres" at the time of the settlers' landing, according to White's account of the journey. Five years later, in 1639, the Surveyor General measured the island and found that it was about 80 acres. It formed part of St. Clement's Manor, which was granted by the Second Lord Baltimore to Dr. Thomas Gerard in 1639. Gerard subsequently became a major landholder and political figure in Maryland and Virginia. After the island became the property of Gerard's daughter Elizabeth, the wife of Nehemiah Blackistone, it became known as Blackistone Island.