Why was the county unit system made

Controversy.  The County Unit System generated great controversy due to the fact that it gave the votes of counties with smaller populations a significantly greater weight than counties with larger populations. For at least the final two decades the system was in use, a majority of statewide unit votes were controlled by counties that, collectively,...

Read the following link and you could find it there

https://en.wikipedia.org/wiki/County_unit_system

answer; the correct answer is (travel horizontally);