Going West

Going West is the main way to progress in the game. There are 60 towns in each Area, so every 60 times you go west, you move to the next Area with different businesses, upgrades, and unlocks. Each town gives pioneers and settlers when completed, except for the last one of each Area, which takes them all away. The population required to go west is based on your Area, town number, and the amount of pioneers you had at the start of that town. Settlers are not considered in the calculation for target population.

The formula for pioneers gained after going west is approximately ((current Area total earnings/1e+6)^0.4375) - (current pioneers + current settlers + total pioneers spent in all towns of the current Area), provided that you don't reset before going west and do not stay in towns after reaching the maximum population. The formula doesn't actually seem to consider the total income in the current Area, but instead considers your current pioneer, settler, and spent pioneer amounts, the amount of population gained from resets in the current town, and cash earned in the current town. So if you reset before going west and/or don't go west before reaching the maximum population on every town, the above formula will not be correct for you, but it's still usually close enough.

The maximum population that can be earned in a town is usually about 8x the target population if you didn't reset before going west in that town, but not always.

The formula for maximum population in a town is approximately (6.5*(sum of owned pioneers, spent pioneers and owned settlers at the start of the current town) + 7.5*the target population before doing any resets in the current town.) - 2*(total pioneers and settlers gained from resets in the current town).

This means that multiple people who went west at maximum population for every town can have a different amount of pioneers and settlers on the last town of the Area, because resetting before going west many times can significantly affect it. Spending pioneers also affects it, but it's negligible.