Frostpunk

This Achievement Requires You To Establish Trade Routes With Hot Springs, Shipwreck Camp, And Children's Mine - And Therefor Should Be Done Towards The End Of A Playthrough.

Preferrably A Playthrough In Which You Are Trying To Get All Settlements To "Loyal"
- The Loyal Status Is Required For A Settlement To Help You And Get This Acheivement.
- I Did This On Endless Mode, But Any Mode With The Three Settlements Should Be Fine.
- Playing On Easy Does Not Void This Achievement

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After You Establish Trade Routes With The Other Settlements
(Make An Outpost Team And Send Them There To Set Up Camp)

Building The Adminstration Building Lets You See Other Settlement's Disposition Towards You.

Starts At Neutral.
Distrustful <- Cautious <- Neutral -> Friendly -> Loyal
(See Guide On Endless Social Activist For Help Making Other Settlements Loyal To You)

Once A Settlement Is Loyal To You -
Occasionally A Settlement Needs Help, Either A Food Stortage Or A Mine Collapse, Etc.
Trade With Them Will Be Unavailable For A Few Days While They Sort This Out.

Usually You Can Send The Supply Of Food, Wood, Or Coal To Them Yourself; Which Ends The Trade Unavailability Early - And Trade Resumes.

However -
Example - A Settlement (Not Hot Springs) Is Having A Food Shortage And Hot Springs Is Loyal To You.
You Will Get The Option To Have Hot Springs Send The Relief Supplies To Them Instead Of You.
- Hot Springs Favor Will Be Exhausted And The Achievement Pops.

The Same Goes For Childrens Mine Helping With Coal And Shipwreck Camp Helping With Wood.

Good Luck!