What is the sphere of influence of a city?

Question

What is the sphere of influence of a city?

Answer 1

The area around a city which it influences in some way.  Chicago has a wide influence stretching perhaps to Rockford, Milwaukee, and other large cities.  It's influence may be as a transportation hub; a performing arts destination; a vacation spot.  Smaller cities within Chicago's sphere of influence affect and influence in different ways:  school systems, local farmer's markets, etc.  One may get down to a small rural settlement whose influence is family history based and must rely on slightly larger towns/cities for shopping, gas, etc.

At one time Rome's sphere of influence stretched from Northern Africa, to the Eastern Mediterranean and beyond, to the British Isles and north into parts of Europe, France and Spain.