(2.1.4) Objective/Resource Hexes: Town and City hexes outlined in gray in Border and Northern states are Objective Hexes. Confed- erate capture of these hexes can generate BPs from the Border States (14.3.3) and VPs for the Northern States (19.3.2). Those outlined in gray in the Confederate states are Resource Hexes. These hexes provide BPs for Confederate Reinforcements (14.3.2).
If you looked up Objective Hexes in the index it would take you to this rule.