Dave, Let's use this page to create a Microscope-Generated timeline. Each bullet point would represent a PERIOD card, with sub-points to represent how they may be modified by an EVENT or SCENE.

BIG PICTURE: Over fifty years, Gotham's original flaws of neglect and greed tear the fabric of the city apart to expose its dark, rotten core

PALETTE: This is a list of things we want in our campaign, and things we don't want. Let's just throw these in a list here for the time being.

We'll take turns adding a PERIOD, an EVENT, or a SCENE.

Let's make the first round of focus be on other heroes and hero groups. The second or third could focus on gangs.

It doesn't matter. Let's just keep hacking away at it. I'm having a great time just freewheeling it.

• HISTORY START : The main gangs of Gotham have taken root and just begin to choke Gotham's prosperity and optimism (DARK)
• Industrial Period : Famous industrialists build infrastructure including roads, sanitation, and most notably bridges in Gotham to try to improve the city's prosperity (LIGHT)
• Immigration Period : Immigration from immigrants from overseas - particularly Italy and China help to fuel the city's growth, but the opportunity also brings more strife (DARK)
• Period of the Victorian Legion : A group of gentlemen adventurers team up to help free Gotham of crime, only to be ultimately defeated and destroyed from without and within (LIGHT)
• The Great Gotham Fire of 1911 a blaze that destroyed a sizeable section of the city and led to a period of civil disorder (DARK)
• The Roaring 20's (LIGHT)
• CAMPAIGN START : The beginning of the campaign in Depression-Era Gotham with all gangs represented (DARK)

https://en.wikipedia.org/wiki/Gotham_City#Fictional_history