What does "strategic importance of a place" mean?

A place can be strategically important for various
reasons. It could be important from a military perspective. For example, a place with
higher elevation will provide you with a good vantage point; a narrow valley will force
the enemy forces to divide and move through in small numbers,
etc. 

Similarly, a place can be strategically important
from a manufacturing point of view. A strategic location may have one or more of these
advantages: availability of cheap labor, raw material, easy and accessible transport,
resources including water and electricity, etc. An example is the East Coast corridor
from Worcester, MA to Providence, Rhode Island; a 45-km stretch that served as the
birthplace of the industrial revolution in the US.

A place
can also be strategically important because of its historic significance and heritage.
An example is Philadelphia. 

Thus, strategic importance
simply refers to some attributes that make a place significant.