Benjamin Bradley was born around 1830 as a slave in Maryland. He was able to read and write. He was put to work in a printing office and at the age of 16 began working with scrap he found, modeling it into a small ship. He continued improving on his creation until he had built a working steam engine, made from a piece of a gun-barrel, pewter, pieces of round steel and some nearby junk. Those around him were amazed by his high level of intelligence that he was placed in a new job, this time at the United States Naval Academy in Annapolis, Maryland.

Despite enjoying his job with the Naval Academy, Bradley had not forgotten his steam engine creation. He used the money he had been able to save from his job as well as the proceeds of the sale of his original engine (to a Naval Academy student) to build a larger model. Eventually, he was able to finish an engine large enough to drive the first steam-powered warship at 16 knots. At the time, because he was a slave, he was unable to secure a patent for his engine. His master did, however, allow him to sell the engine and he used that money to purchase his freedom.

source: http://blackinventor.com/benjamin-bradley/