Burwell died suddenly in 1813 and for nearly thirty years this architectural masterpiece remained unfinished. Fortunately, a Burwell descendant, Major Hugh Mortimer Nelson, purchased the LONG BRANCH mansion in 1842 and finished the interior using elaborate woodwork based on the design published by architect Minard Lafever. A spectacular spiral staircase, spanning all three floors, provided a sense of drama and allowed light to pour in from the belvedere, which crowns the mansion.

Although the descendants of Nelson and subsequent owners, notably Abram Hewitt, made valiant efforts to maintain LONG BRANCH, it's condition had declined by the late 20th century. In 1986, Harry Z Isaacs, a Baltimore textile executive, purchased the estate at public auction. His good taste, remarkable energy, and sizable fortune revitalized the manor house in less than three years. The original woodwork was painstakingly restored, ten of the eleven fireplaces were put in perfect working order, and a west wing was added to balance the facade.