The first USS Miantonomoh was the lead ship of her class of four ironclad monitors built for the United States Navy during the American Civil War.

Completed after the war ended in May 1865, the ship made one cruise off the East Coast before she began a voyage across the North Atlantic in May 1866 to conduct a lengthy showing the flag mission in Europe.

[3] Miantonomoh was powered by a pair of horizontal horizontal-return connecting-rod steam engines designed by the Engineer-in-Chief of the Navy, Benjamin F. Isherwood.

[5] Her main battery consisted of four smoothbore, muzzle-loading, 15-inch (381 mm) Dahlgren guns mounted in two twin-gun turrets, one each fore and aft of the single funnel.

[3] A 5-by-15-inch (127 by 381 mm) soft iron band was fitted around the base of the turrets to prevent shells and fragments from jamming them as had happened during the First Battle of Charleston Harbor in April 1863.

There Miantonomoh embarked the Assistant Secretary of the Navy, Gustavus Fox on 3 June and the British naval attaché, Captain John Bythesea, VC.

[8] The voyage was also intended to reciprocate lengthy visits by squadrons of the Imperial Russian Navy to New York and San Francisco during the Civil War and to enhance the prestige of the United States among the European powers.

[12] After reaching Queenstown on 16 June, where the ships were met by the British broadside ironclads Achilles and Black Prince, they proceeded to Portsmouth, arriving on the 23rd.

Beaumont, Bythesea and Fox gave a guided tour to the Board of Admiralty and the inventor of a different type of armored turret, Captain Cowper Coles, on 29 June before her departure for France.

They steamed via the Canary and Cape Verde Islands, Caribbean ports and the Bahamas, before the monitor arrived at Philadelphia on 22 July, thus completing a cruise of more than 17,700 nautical miles (32,800 km; 20,400 mi).