The Longworth House Office Building Post Office is quite simply the best US Post Office I have encountered anywhere. The lines move quickly, the staff is friendly and they always have an abundance of stamps and mailing supplies. Mail is dispatched in the morning and after 4:00 p,m, in the afternoon. Staff will provide a special manual cancellation if you ask for it. The post office is located in the basement of the Longworth Building, but is open to the public. You will have to go through security upon entering the Capitol complex. It is easily reached by tunnel from the Cannon and Rayburn buildings. read more