When the Civil War started, the greatest prize for either side was Kentucky. Kentucky had declared itself neutral as the War began, but the state was too valuable to be left alone. The Ohio river was a perfect border and the state had valuable food and man power. Most importantly the Ohio, Mississippi, Cumberland, and Tennessee all flowed in Kentucky. These rivers were essential supply lines and troop transports. Lincoln understood the importance of his native state when he said, “I hope to have God on my side, but I must have Kentucky.” The South invaded the state on September 5, 1861, there after Kentucky voted to side with the Union.
Kentucky during this time is a fascinating story, there is a really great book on this subject that I know of.
Historically Speaking 