Much depends on how large or important your city is for how easy or difficult it will be to find information about a city. Encyclopedia Britannica and CREDO Reference -- and others, see the tab for Encyclopedias and Almanacs, above -- are good for basic information for just about all cities.
List of Cities - Wikipedia has starting points for many sources of information on a particular city grouped in different ways.
CityLab News stories and maps. "CityLab is committed to telling the story of the world’s cities: how they work, the challenges they face, and the solutions they need."
Most city governments have a department or office dedicated to business or economic development with a web site that will point you to data and statistics on what is best about a city. Search Google for your city and the phrase "economic development" or "business development". For example Chicago and economic development (The office for the city of Philadelphia uses the term "Commerce".)
Policy Map is a web-based Geographic Information System that provides a simple mechanism for visualizing data. Available data includes demographics, home sale statistics, health data, mortgage trends, school performance scores and labor data like unemployment, crime statistics and city crime rates.
