After the Vanderbilts divorced in 1895, Alva married Oliver Hazard Perry Belmont, moving down the street to Belcourt. After his death, she reopened Marble House and added a Chinese Tea House on its seaside cliffs, where she hosted rallies for women's suffrage. She sold the house to Frederick H. Prince in 1932. Prince's estate gave the house and its furnishings to the Preservation Society of Newport County in 1963.

In 1971 it was added to the National Register of Historic Places. Five years later the Department of the Interior designated it, and the Bellevue Avenue Historic District in which it is located, as National Historic Landmarks.