Following Armstrong's death in 1900, his heirs struggled to maintain the house and estate. In 1910, the best of Armstrong's art collection was sold off, and by the 1970s, in an attempt to meet inheritance tax, plans were submitted for large-scale residential development of the estate. In 1971 the National Trust asked the architectural historian Mark Girouard to compile a gazetteer of the most important Victorian houses in Britain which the Trust should seek to save should they ever be sold. Girouard placed Cragside at the top of the list; in 1977, the house was acquired by the Trust with the aid of a grant from the National Land Fund. A Grade I listed building since 1953, Cragside has been open to the public since 1979.