Local Department is a building added in the Seat of Power DLC. Similar to the palace, it affects and boosts buildings built within the street range of the local department, which is equal to half of the range of the palace itself.
In opposite to the palace, in a local department you can choose only one department and one policy from chosen department. Nearby buildings will be boosted both by the passive effect of the department (depending on the main palace's prestige level) and the active effect of the policy. The department and policy must be unlocked first in the palace. Policies chosen in local departments are independent from the policy selected in the palace, i.e. policies in each local department can be different from each other and from the policy chosen in the palace.
Number of local departments is limited to one local department per island.