No example of civic pride is too trivial for the Arlington Historical Museum. While roughly a third of the space goes to the city’s founding and role in the Civil War, there’s also a display case entirely devoted to a letter from Ronald Reagan to a kindergarten class in 1981 (thanking the students for a get-well note sent after his near-assassination), the pen used to write it, a poster-sized version of the letter, pictures of the kids, a portrait of Reagan and two newspaper clippings.