If you want to add a 'modern' political issue you could add a dynamic where city growth results in a backlash from "original" city participants who push for laws/policies to keep the city the 'same', increasing real estate prices, zoning issues, subsequent gentrification as no new internal growth pushes the wealthy out into low income housing areas, lack of low income housing as it can't keep up with gentrification (or development of low income housing lacks profitability due to laws like rent control or other well intentioned laws), and generally hampers growth and increases conflict/unhappiness within the cities.