"A town is a small city (Level 1 to 3). It is too small to be able to forward Supply during the Supply Distribution Phase unless a Depot has been built in the town"
As far as I can tell the only depot in the wild west is the one in Denver. And ALL the cities west of Missouri are < 3.
Therefore zero supplies are pushed or will be arriving to the west (from let's say Missouri).
A chain of depots could be built. I see two possible routes:
1) southern route - through Kansas: in game closest depot in Lexington (MO)
2) northern route - through Nebraska: in game closest depot in Council Bluffs (IA)
I more or less calculated that to push supplies to the west you should need minimum 3 depots (northern or southern routes) to link Lexington or Council Bluffs with Denver: $ 240.000 (3 wagon trains).
Then you should need another chain of depots from north (Denver) to south (let's say Fort Craig and Fort Stanton in NM). I guess minimum 3 = $ 240.000.
So that makes 240.000 x 2 = $ 480.000
And finally there are more expenses: the units you need to protect these depots, lines of communication.
Is this more or less correct?
And finally: the boxes in the left side of the screen (California, etc.): will they push supplies to the on map areas?
On the screenshot, the depots are randomly placed, for the sake of the argument. I calculated 3 depots are needed. But maybe 4 are the correct number.
