Assigned to the North Atlantic Fleet, Missouri left Norfolk, Virginia, on 4 February 1904 for trials off the Virginia Capes and fleet operations in the Caribbean Sea.
On 13 April, during target practice, a flareback from the port gun in
her after turret ignited a powder charge and set off two others. No
explosion occurred but the rapid burning of the powder suffocated 36 of
the crew. Prompt action prevented the loss of the warship and three of
her crew earned Medals of Honor for extraordinary heroism. After repairs at Newport News, Missouri sailed on 9 June for duty in the Mediterranean Sea from which she returned to New York on 17 December.
Fleet operations along the east coast and in the Caribbean during
the next years were highlighted by her relief to earthquake victims at Kingston, Jamaica, from 17 January to 19 January 1907. In April she took part in the Jamestown Exposition.
With the "Great White Fleet," Missouri sailed from Hampton Roads on 16 December 1907, passing in review before President Theodore Roosevelt
at the beginning of a world cruise which was to show the world that
American naval might could penetrate any waters. Calling at ports in
the Caribbean and along the east coast of South America, the fleet
rounded Cape Horn to call in Peru and Mexico before arriving at San Francisco, California, on 6 May 1908 for a gala visit. In July the fleet turned west for Honolulu, Hawaii, thence to New Zealand and Australia, arriving in Manila on 2 October. The most tumultuous welcome yet came in Yokohama, Japan, and with a call in Amoy, China, the fleet began the passage home by way of Ceylon, Suez, and ports in the eastern Mediterranean. Departing Gibraltar
on 6 February 1909, the fleet was again reviewed by President Roosevelt
upon its triumphant return to Hampton Roads 22 February. An important
diplomatic mission had been carried out with the greatest success.
Placed in reserve at Boston, Massachusetts, on 1 May 1910, Missouri
recommissioned on 1 June 1911 and resumed east coast and Caribbean
operations with the Atlantic Fleet. In June 1912 she carried Marines from New York to Cuba
where they protected American interests during a rebellion. The next
month the battleship carried midshipmen for training then
decommissioned at Philadelphia, Pennsylvania, on 9 September 1912.
Missouri recommissioned 16 March 1914 for that summer's United States Naval Academy
Practice Squadron's cruise to Italian and English ports. She returned
to ordinary at Philadelphia 2 December 1914, but recommissioned 16
April 1915 to train midshipman in the Caribbean and on a cruise through
the Panama Canal to California
ports. She returned to the Reserve Fleet at Philadelphia 18 October
1915, recommissioned 2 May 1916, and again conducted training along the
east coast and in the Caribbean until placed in ordinary for the winter
Upon the entry of the United States into World War I, Missouri recommissioned 23 April 1917, joined the Atlantic Fleet at Yorktown, Virginia, and operated as a training ship in the Chesapeake Bay area. On 26 August 1917 Rear Admiral Hugh Rodman broke his flag in Missouri
as Commander, Division 2, Atlantic Fleet, and the warship continued to
train thousands of recruits in engineering and gunnery for foreign
service on warships and as armed guards for merchant vessels.