No Settlement can reach Rank 7 without a Mid-Town district. Belonging to the Department of Interior, the Mid-Town is primarily dedicated to administrating your growing city. Building it unlocks the optional R7 districts and your ability to move on to Rank 8 through the Downtown district.
Action - Keep the Peace
Keep the Peace allows civic-minded player to contribute to their community. If a Mid-Town district is built in their settlement, players can visit and act as an impromptu voluntary police force. This action not only reinforces Security in the Mid-Town but comforts the local Yeomen immensely. Seeing this display of public safety causes a few more Yeomen to move in each time Keep the Peace is performed.
Main - Town Hall
The Town Hall is there for your bureaucratic needs. Every level of Town Hall increases the taxes you get back from resident Nobles in your settlement. Simply by being a centralized paperwork hub, the building decreases Paper upkeep throughout the settlement. To top it all off, the Town Hall also processes wood Pulp into Paper, supplying the endless bureaucratic consumption of the stuff.
Exclusive - Civil Administration
The effect of the Civil Administration buildings are only evident to those looking at the big picture. It's primary function is to reduce the Upkeep requirement of all Main buildings. This means the central building of every district will cost less to maintain. All the paperwork done in the Civil Administration has a beneficial effect on transportation risks. Keeping track of losses helps to reduce the overall Transport Loss Chance for everyone in the settlement. Building a Civil Administration costs only Paper and Dyes so it's a pretty good deal.
Linked - Apartment Building
The Apartment Building is your primary source of Yeoman housing. They are most efficient in the Mid-Town district but can be built anywhere. These stacked residences are built of Bricks and Canvas, requiring a fairly developed city in order to build them in mass. Providing more than a hundred Yeomen per building level of each Apartment, this is the most efficient of your Linked Yeomen housing.
Minister - Lord Mayor
The Lord Mayor is an inevitable seat in the Department of Interior. They are supported by the Mayoral Office (ministry). This team together faces the true mass of civil administrating. This can be represented in tons of paperwork processed through the hands of intelligent and thoughtful clerks. Just keeping track of everything in a rank 7 settlement is a huge job and the Mayor must be up to it.