The halfway point between Indianapolis and Gary, Indiana, is in Lafayette, Indiana.
According to MapQuest.com, if you are traveling on I-65 and I-70, the halfway point is Indianapolis, Indiana. The whole trip is 356.50 miles, and Indianapolis is 175 miles between the two.
Corbin, KY
You would be about 2 miles west of Coalton KY on I64
What is halfway driving between Lansing, Michigan and Augusta, Maine
Habersham, Georgia is exactly halfway but Atlanta has more hotel and restaurant options.
Jewell Village, Indiana is the halfway point from Lansing, MI to Columbia, TN. The closest major city that is roughly halfway is Indianapolis, IN.
Bettendorf, IA but anywhere in the Quad Cities would be fine.
If judging points from Tallahassee, Florida to Louisville, Indiana (on the Indiana/Kentucky Border). The halfway point would be around Chattanooga, Tennessee If judging points from Orlando, Florida to Indianapolis, Indiana the halfway point would be Around Atlanta, Georgia.
Round Grove, IN. You might as well go on to Lafayette.
Prospect, TN
Since you don't give specific cities, we'll arbitrarily say "Indianapolis to Trenton". The halfway point is the Ohio/Pennsylvania state line.