Complex sentence: The Hotel Del Monte was a large resort hotel in Monterey, California from its opening in 1880 until 1942 when during World War II it closed and the building leased to the Naval Postgraduate School of the United States Navy.
Split into simpler sentences: The Hotel Del Monte was a large resort hotel in Monterey, California from its opening in 1880 until 1942. Later the Hotel Del Monte became the Naval Postgraduate School of the United States Navy.