Not everyone loves the capital of the United States. To Ulysses S Grant, it was a ‘pestilential swamp’; to novelist Gore Vidal, a ‘city of the dead’. It is true that Washington still has its problems. The District of Columbia has the highest crime rate in the United States, and the statistics for violent crime are more than twice the national figure. Its climate also tends to extremes: summers are often unbearably humid, and winters can be savage. If you can manage such hazards, however, the city has a great deal to offer visitors, and particularly to those interested in American history...