Trump Billionaires Club has six city boards in total:

1. New York City (the starting city)
2. San Francisco
3. West Palm Beach
4. Dallas
5. Las Vegas
6. Washington DC

You unlock the next city by progressing through the current one — completing achievements, building businesses, and reaching the required Player Level. Each new city introduces fresh business types and (in some cases) board-specific tiles like the Oil/Refinery split in Dallas or the Lobbying business in Washington DC.