Rockville ranked in the top 5% of small cities in the U.S., and the best small city in Maryland, according to a WalletHub comparison published Tuesday. To calculate which city was best to live in, WalletHub compared 1,318 cities with population sizes between 25,000 and 100,00, based on 45 metrics across five topics: affordability; economic health; education and health; quality of life; and safety, according to its methodology.