Updated 16 October 2010

USS New Hampshire B-25 in December 1910
An overall view showing the multiple calibers used on USN pre-dreadnoughts.  Forward and aft are 12" (30.5 cm) main gun turrets, the amidships turrets have 8" (20.3 cm) guns, there are 7" (17.8 cm) guns in the hull casemates and 3" (7.62 cm) guns in the superstructure casemates.
U.S. Naval Historical Center Photograph # NH 73979

7"/45 (17.8 cm) on Tractor Mount at Dahlgren Naval Proving Ground, Virginia
This weapon is listed as being the first gun ever fired at Naval Weapons Station Dahlgren, an event which took place on 16 October 1918
U.S. Navy Photograph No. 090722-N-0000X-001

The same tractor mounting as shown above being off-loaded at the Naval Surface Warfare Center Dahlgren Division
This weapon will be reconditioned and placed on display during Rear Adm. John Dahlgren's 200th birthday commemoration which is scheduled for 13 November 2009
U.S. Navy Photograph No. 090720-N-6148D-001

7"/45 (17.8 cm) "South Gun" now at Ft. Derussy at Pearl Harbor, Hawaii
Note projectile at right
Photograph copyrighted by Charles Bugajsky

7"/45 (17.8 cm) "North Gun" now at Ft. Derussy at Pearl Harbor, Hawaii
The "North" and "South" guns at this fort were originally from USS New Hampshire (B-25)
Photograph copyrighted by Charles Bugajsky

Another view of the 7"/45 (17.8 cm) "South Gun"
Photograph copyrighted by Charles Bugajsky

7"/45 (17.8 cm) being used as a railway gun at Camp Eustis, Virginia
Photograph courtesy of The Mariners' Museum

7" (17.8 cm) AP Projectiles used during World War II

06 September 2009 - New pictures of mobile tractor mounting
16 October 2010 - Added picture of railway mounting