This is only achievable once the Player has achieved the Trade Reputation of "Chairman", requiring you to keep accumulating Piastres on person (1 million Piastres) to unlock Chairman.
Once this Trade reputation is reached, the player may then proceed to build 100 Enterprises. This does not include Urban Buildings! The Player must purchase either Resource Production or Town Manufactures for them to be counted as "Enterprises"
Once you cannot purchase anymore enterprises, head to the next town and repeat until you have purchased 100 Enterprises, unlocking the achievement