Tennessee, Virginia, Arkansas, and North Carolina all bordered at least one Union state.
Tennessee shared a border with Kentucky, which remained a Union state in the Civil War.
Virginia bordered 4 Union states: Missouri, West Virginia, Kentucky, and Maryland.
Arkansas bordered Missouri; however, Missouri had Union and Confederate territories.
North Carolina bordered Virginia, which like Missouri, had both Union and Confederate territories.
The aforementioned Confederate states lied right at the Confederate boundaries; some bordered places with territories of both sides of the Civil War.