Numerous spaces in the interior of the building were designed in several styles by decorators such as Louis Comfort Tiffany, Stanford White, Kimbel and Cabus, Alexander Roux, Francis Davis Millet, and the Herter Brothers. These include halls and stairways; a series of regimental rooms on the first floor; and twelve rooms for the 7th Regiment's companies on the second floor. The drill hall, measuring , was one of New York City's largest column-free indoor spaces when completed.
The interior design of the building included numerous spaces with various styles by decorators like Louis Comfort Tiffany, Stanford White, Kimbel and Cabus, Alexander Roux, Francis Davis Millet, and the Herter Brothers. These included halls and stairways, a series of regimental rooms on the first floor, and twelve rooms for the 7th Regiment's companies on the second floor. The drill hall was one of New York City's largest column-free indoor spaces upon completion.