Simplify the following text for a Grade 10 native English-speaking person.
Original: The Secretary of the Treasury of the United States is the head of the United States Department of the Treasury , which is concerned with financial and monetary matters , and , until 2003 , also with some issues of national security and defense .
Simplified: The United States Secretary of the Treasury is the head of the United States Department of the Treasury . He is concerned with finance and monetary matters , and , until 2003 , some issues of national security and defense .