The Union states that were isolated geographically from the rest of the Union during the American Civil War included primarily the far western states of California and Oregon. These states were separated from the main body of Union states by vast distances and Confederate-controlled or contested territories

. Additionally, the Border States-Delaware, Maryland, Kentucky, Missouri, and West Virginia-were Union states that had divided loyalties and complex situations. While they did not secede, they were surrounded by Confederate states or had significant Confederate sympathies, which made them somewhat isolated politically and militarily from the core Union states

. In summary:

• Isolated by geography: California and Oregon were physically distant from the main Union states.
• Border States with divided loyalties: Delaware, Maryland, Kentucky, Missouri, and West Virginia were Union states but were politically and militarily isolated due to their proximity to Confederate states and internal divisions

These Border States were crucial to the Union's strategic interests, especially Maryland and Kentucky, because their loss would have jeopardized the Union capital and other key regions