USS Chicago -- armament

37 mm and 47 mm cannons on USS Chicago.
John Alden’s book -- The American Steel Navy-- confirms that Chicago had two 37 mm and four 47mm Hotchkiss revolving cannons.
Additional drawings of naval armament may be available from the National Archives in Washington, DC, in the Records of the Bureau of Ordnance.

Contact information for the National Archives is as follows :

Old Military and Civil Records Branch
National Archives and Records Administration
700 Pennsylvania Avenue NW
Washington, DC 20408
1-866-272-6272 http://www.archives.gov/contact/