Who is Smithsonian institute named for?

A guy named James Smithson (who actually never set foot in the U.S; he lived in France) wrote in a will that his nephew was to have 500,000 with the idea that he would pass it on to his children and so forth. If the nephew never had children the U.S. got the money. James Smithson died three years later, and his nephew died six years later without any children. Then the U.S. got the money and built a museum named after Smithson. No one knows why James Smithson wrote the money to the U.S.