This minimal mod adds two buttons to the district panel:

• Set Historical: Make all currently existing buildings in the district historical
• Unset Historical: Unset the historical status of all buildings in the district
  

It's basically just a batch command that toggles the "Historical" checkbox for all buildings in a district.

It only affects the currently existing buildings in a district, so if there are empty zones, new buildings can still grow there.


What does "Historical" mean?

The "Historical" checkbox is a recently added feature in the building info panel of the game. When checked, a growable building will not be replaced with a higher level building on upgrade. The inhabitants will still level up like normally.

There were also mods that offered a similar functionality, such as Control Building Level Up, but these have a significant disadvantage: They prevent the building from level up, that means your inhabitants will not gain a higher wealth/education level and your city will not progress.

Of course, historical buildings can still burn down or be destroyed by disasters.


Incompatibilities

Compatible with Building Themes and similar mods as it only adds to the UI and doesn't alter the simulation logic in any way.

Plop the Growables in "Make all historical" and "Make all not historical" mode will override the value of the checkbox, so this mod will not have any effect.

The mod can be safely disabled at any time without causing harm to your city.

This mod was request by QuadRioters. Make sure to check out his workshop if you like futuristic assets :)

Source