Outside a few cities, you'll need a car

New York, Chicago, Washington, Boston, and San Francisco work well without a car. Almost everywhere else, distances are long and transit is thin, and the national parks are only reachable by road. Book rental cars early for summer and holidays, add the toll transponder if you'll drive the Northeast or Florida, and remember that drivers under 25 pay extra fees with most companies. Gas is sold by the gallon and prices vary a lot by state.