Powell was in his time one of the most famous history painters of the United States. He is best known for his painting "the Discovery of the Mississippi by De Soto A.D. 1541" in the Capitol Rotunda.Here he depicted Columbus defending his plans before the Council of Salamanca. It’s one of these typical history paintings with well arranged groups of persons and an illumination like on a stage.
But the real interesting thing is that Columbus is in a very similar pose like the then so popular anticlerical heroes Luther or Galileo. His clerical adversaries rely on books, Columbus instead stands alone only supported by his maps. He’s a modern man fighting against religious ignorance. And that for Powell is claiming him as a real American hero.