Setback requirements and other restrictions, written into the lot deeds of the newly filled Back Bay, produced harmonious rows of dignified three- and four-story residential brownstones (though most along Newbury Street are now in commercial use). The Back Bay is listed on the National Register of Historic Places, and is considered one of the best-preserved examples of 19th-century urban architecture in the United States. In 1966, the Massachusetts Legislature, "to safeguard the heritage of the city of Boston by preventing the despoliation" of the Back Bay, created the Back Bay Architectural District to regulate exterior changes to Back Bay buildings.