They were all on the outskirt of the two sides and every one of them had motivations to go both routes in the contention.
Maryland was a slave state and from multiple points of view held to an indistinguishable thoughts from the Confederates. The most compelling motivation that they went poorly them is on the grounds that the US government ensured there were a lot of troops there, so Washington DC wasn't cut off amidst Confederate land.
Both Missouri and Kentucky had their own smaller than expected form of the Civil War going, where neighbors battled with neighbors.
Fertile Crescent should be your answer, The earliest farmers lived in the Fertile Crescent, a region in the Middle East including modern-day Iraq, Jordan, Syria, Israel, Palestine, southeastern Turkey and western Iran.
The main reason was because of over population in a small confined area. They also moved father out west so they could get more materials or supplies.
One of the major things that led to the collapse of the German army/navy and their war effort was internal fighting among the Germans themselves regarding tactics.
