The United States Merchant Marine is comprised of civilian mariners and a fleet of U.S. civilian and federally owned merchant vessels. These fleets are managed by either the government or private sector, and engage in commerce or transportation of goods and services in and out of the navigable waters of the United States. The Merchant Marine is responsible for transporting cargo and passengers during peacetime. In time of war, the Merchant Marine can be an auxiliary to the Navy, and can be called upon to deliver military personnel and materiel for the military.

In the Second World War, OVER 3 million tons of merchant ships were lost. Merchant Mariners died at a rate of 1 in 24, which was the highest rate of casualties of any service.  733 American cargo ships were lost and 8,651 of the 215,000 who served in the US Merchant Marine perished in troubled waters and off enemy shores.

During the Korean War, the number of ships under charter grew from 6 to 255. 

During the Vietnam War, ships crewed by civilian seamen carried 95% of the supplies used by the American armed forces. Many of these ships sailed into combat zones under fire.

During the first Gulf War, the merchant ships of the Military Sealift Command (MSC) delivered more than 11 million metric tons of vehicles, helicopters, ammunition, fuel and other supplies and equipment.   

The motto of the US Merchant Marine Academy is:  "Deeds, Not Words"