John F. Kennedy did serve as a Representative from the 11th Congressional district of Massachusetts in the House from 1 January 1947 to 3 January 1953. He occupied what was then called 322 Old House Office Building which currently is comprised of rooms from the current office suites of 317 Cannon House Office Building (Representative Kathy Castor of Florida’s office) and 315 Cannon House Office Building (Representative Zach Space of Ohio’s office).
Below is a December 1951 photo from the Library of Congress of Representative John F. Kennedy doing a “Meet the Press” talk with one of its founding members to his right, Ms. Martha Rountree.