From the record
“The Callaghan Apartments, also known as the Plaza Apartments and Hotel and the Plaza Hotel, was erected in 1918 in Hot Springs State Park in Thermopolis, Wyoming. It was at one time one of six hotels catering to tourists using the Big Spring of Thermopolis, a hot spring reputed to possess curative properties.”
Wikipedia article Callaghan Apartments, CC BY-SA 4.0.
One of 12 National Register listings published here for Hot Springs County · listed in 1993 · category: Building.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service

