"Il" is the postal abbreviation for "Illinois" in the US, and the US is located in the Western Hemisphere.
As a part of Illinois it became a part of the US on 3 December 1818.
western
Western Hemisphere.
western part
It is a city within the US State of Illinois.
western part
the correct answer is Western
The Mississippi River forms the western border of Illinois.
Western
Western part of the United States
The same year as the rest of Illinois, in 1818.