Servius Tullius created the first census and assigned the population in classes according to their wealth (mainly based on how much armor a man could afford).  The rich would have to serve in the army, and the poor would not have to.  However, the rich would get the first say in the government.  If they could not reach a consensus, the next class would vote.  He added two more hills to Rome, the Quirinal and the Viminal because there were so many people.  He built a wall around the seven hills of Rome.  He also constructed a temple to Diana of Ephesus because it would symbolize union with the Latin people.  At first he was not ruling by the consent of the plebs, but he changed that, and conquered more land for their sake. 

Classes in the Army

First Class (100000+ sesterces)-helmet, round shield, greaves, coat of mail, spear, sword

Second Class (75000-100000 sesterces)-helmet, buckler, greaves, spear, sword

Third Class (50000+ sesterces)-helmet, buckler, greaves, spear, sword

Fourth Class (25000+ sesterces)-spear, short javelin

Fifth Class (11000+ sesterces)-slings and stones

Proletarian Class (0-11000 sesterces)-did not have to serve in the military

Calvarly-High ranked men with horses given by the state, and the widows pay for the horses