The National Sanitarium was located next to the Hill-Cohn Sanitarium at the corner of Morgan and Mulberry Streets in Martinsville. The National was originally the Cottage Hotel, built by Wilbur E. Rose in 1894, and in 1895 the building was converted into a health spa and renamed by new owners Dr. Edward M. Sweet and Isaac Nutter.

      The National Sanitarium catered to a respectable but not wealthy clientele. According to The Martinsville Democrat in 1915, it was popular with businessmen. The impressive but relatively small two-story frame building was reminiscent of a southern plantation house with encircling porches on both levels. It was lighted by gas and electricity and included 30 steam-heated guest rooms, and a menu of mineral baths in imported porcelain bathtubs at a cost of $5 per week for each person. The spa offered a menu of hot, cold, vapor, electric, mud, and Turkish baths. Baths alone were 50 cents each. The more expensive rooms, at $8 per week, included medical care. The spa was renovated and enlarged in 1907 and renovated in 1933 with new hardwood floors, brick wainscoting, steam and shower rooms, and terrazzo floors in the bath rooms. In 1935 an advertisement mentioned that the spa contained a tavern.

     Dr. Sweet sold the business in 1935, and later owners included Jap Jones, Sam Barskin, Clyde Grass, and Dr. Simon P. Scherer. The spa soon closed due to several factors affecting the sanitarium industry of that time and area of Indiana. The building was bought by the Schnaiter Lumber Company in 1937. Fire destroyed the old National Sanitarium building on the morning of March 24, 1944. Local resident Peter Gates was killed in the fire, making it the first sanitarium fire in Martinsville to claim any casualties. The site is currently occupied by a John Hubler Chrysler-Dodge car dealership.