A series of Kings advanced the Roman City-state to the level of a Republic by civil wars and revolts.
Romulus ruled as the first of a line of kings of Rome from 753 BC to 715 BC.  He populated Rome with fugitives from other tribes and wives abducted from the Sabine tribe.  Known as the warrior-king, he developed Rome’s first army while expanding Rome’s territory.  He is credited with the establishment of the patrician and plebian political classes and the foundation for the Roman Senate.
The 2nd King, Numa Pomplious, a Sabine, ruled 715 BC to 673 BC and was credited with the organization of most of the Roman religious rites and offices.  His reign was one of peace and religious reflection.
Tullius Hostilues, the 3rd King, ruled 672 to 641 BC.  His philosophy was completely opposite to that of his predecessor.  In his view, Rome had lapsed into senility.  His reign became one of conquest and expansion including the destruction of a rival city, Alba Longa.  Hostilus combined administrative ability with military achievement while conquering and absorbing several Latin tribes.
According to lore, because of Hostilius’ warlike behavior and the spread of the plague, he was struck down by a lightning bolt.  The Senate chose Angus Marcius as the 4th King (640 to 616 BC).  He is credited with the formation of the plebian class citizen – a step toward democracy.  He built the first bridge across the Tiber. 
The 5th King Marcius Priscus (Tarquinius I) was the 1st Etruscan monarch (616 – 579 BC).  His reign is credited with the Roman Games, the Circus Maximas, and the construction of the great sewers (cloacae).  These operations were “funded” through the conquest of additional Latin and Sabine tribes.  Much of Rome’s military symbolism and civil offices are believed to have been created during this period.  He is also credited with bringing Etruscan “military triumph tradition” to Rome.  His death was at the hands of the sons of Marcius. 
Serfiius Tullius ruled as the 6th King from 578 to 534 BC.  He is renowned for designing a new constitution further defining the citizen classes and their legal rights.  The Servian Walls (Defensive City Walls of Rome) are attributed to him.  He was assassinated by his daughter and her husband, Tarquiinus
The 7th and final King of Rome, Tarquinius Superbus  (Tarquin the Proud) ruled from 535 to 510 BC.  The Etruscans were at the height of their power, the authority of the Monarchy was absolute.  He repealed several constitutional reforms and used violence and murder to retain his power.  His tyrannical rule was feared and hated by the Romans.  The Tarquinus and the Monarchy were driven from Rome in 510 BC by a violent revolt led by Lucius Junius Brutus and Lucius Tarqinius Collatinus.
The Senate voted to never again permit rule by a King and formed a Republic Government in 509 BC.  Brutus and Collatinus were elected the first Consuls of the new republican government.
Free from the rule by Kings, The Romans developed a strict social status hierarchy and Senate that would provide the political power and institution for the conquest of the Western World.