In 1885, William C. Endicott, President Grover Cleveland's Secretary of War, was tasked with creating the Board of Fortifications to review seacoast defenses.The findings of the board illustrated a grim picture of existing defenses in its 1886 report and recommended a massive $127 million construction program of breech-loading cannons, mortars, floating batteries, and submarine mines for some 29 locations on the US coastline.Within a few years, it was realized that operating the disappearing carriage negatively impacted the rate of fire, and the M1900 low-profile pedestal mount was designed.To quickly arm some works a few weapons were purchased from the United Kingdom including nine 6-inch Armstrong guns, two of which survive at Fort DeSoto near St. Petersburg, Florida.Between the Endicott program and the 1905–15 Taft Board fortifications, approximately 200 6-inch guns were emplaced in the United States and its possessions, around 150 of which were on disappearing carriages.Many 6-inch weapons (most of them stored since World War I) were remounted on M1 through M4 shielded barbette carriages at new locations in two-gun batteries to complement the 16-inch guns.[13] Some additional 6"/50 caliber ex-Navy guns were mounted in the year after Pearl Harbor to provide some defense while the new batteries were under construction; locations included Alaska, American Samoa, and Suriname (formerly Dutch Guiana) among others.
6-inch M1900 gun on M1900 pedestal mount, annotated
Two 6-inch guns on an M1917 carriage (foreground) and an M1917A carriage (background) in early 1919.
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Annotated photograph of an M1901 Buffington–Crozier disappearing carriage for an M1900 12-inch gun, generally similar to 6-inch disappearing carriages
Battery 245 at Fort Stevens, Oregon, two 6-inch guns on shielded barbette carriages, built in World War II. The battery's ammunition and fire control bunker is behind the gun.
Typical entrance to 6-inch ammunition bunker at Fort Ebey, Washington state