The number 1 best place to visit in the United States according to myself and TripAdvisor, is San Francisco, California. Some of the things San Francisco has to offer includes exploring Fisherman's Wharf and the world renown Aquarium of the Bay, ride a cable car, stroll around the Presidio, walk the Golden Gate Bridge, and by night hit some of the best clubs on the West Coast. The best time to visit San Francisco is from September to November. This season offers warm temperatures and fewer crowds. Spring is another good time but a colder breeze is more present. When I visited San Francisco my favorite experience was touring Alcatraz prison, the prison is located on its own island and has a lot of history. Also, driving the mountains surrounding San Francisco Bay to get a better view of the Golden Gate Bridge and City was a great experience.
Number 1 worst place to visit in the United States is Detroit, Michigan. Detroit used to be the fourth largest city in the United States, it is now the 10th largest. The city lost a large majority of its population do to having one of the highest unemployment rates in the nation. There are plenty of abandoned buildings, abandoned houses, and abandoned factories throughout the city, and also has a large amount of urban decay. Crime in the city is an issue as it has been for many years. I have never personally been to Detroit, Michigan, but from what others have said about its danger, I may not have a desire to visit the city. Although, I am sure just like any other large city, Detroit is going to have its dangerous sides and safe sides.