Short answers, pulled from the story.
The first wartime role of an identifiable United States Merchant Marine took place on the 12th of June 1775 at the Battle of Machias. A group of Machias residents captured the British supply sloop HMS Margaretta following news of the Battles of Lexington and Concord.
Between 1939 and 1945, 9,521 merchant mariners died in service. This casualty rate was greater per capita than that of each U.S. Armed Forces branch.
As of the 31st of December 2016, the United States merchant fleet had 175 privately owned, oceangoing, self-propelled vessels of 1,000 gross register tons and above. Of these vessels, 114 were dry cargo ships and 61 were tankers.
Maritime academies include the federal United States Merchant Marine Academy in Kings Point, New York; Maine Maritime Academy in Castine; Massachusetts Maritime Academy in Buzzard's Bay; State University of New York Maritime College in the Bronx; Texas Maritime Academy in Galveston; California Maritime Academy in Vallejo; and Great Lakes Maritime Academy in Traverse City, Michigan.
The full name of the Seaman's Act is Act to Promote the Welfare of American Seamen in the Merchant Marine of the United States, which was passed on the 4th of March 1915. This legislation abolished imprisonment for desertion and regulated working hours, food quality, wages, and safety standards.