In 461/0 BC, Perikles' main rival Kimon was driven into exile, and his main political ally Ephialtes (no, not that Ephialtes) was assassinated. It's generally assumed that these two events put Perikles in a position of supreme political power at Athens. He was briefly removed from office in 430/29 due to doubts over the effectiveness of his strategy against Sparta in the Peloponnesian War, but he was immediately re-elected to the generalship a few months later. He remained in charge until he caught the plague and died in 429 BC. His control over the Athenian state lasted about 32 years.

Most of Perikles' reign falls within the period known as the pentekontaetia, the "fifty years" between the Persian invasion of Greece (480-479 BC) and the outbreak of the Peloponnesian War (431 BC). Our sources for this period are sadly thin, but we know that Perikles spent most of his time strengthening the democratic features of the Athenian constitution, extending the Athenian empire abroad, and using the tribute paid by Athens' subjects to build magnificent buildings such as the Parthenon. I've written about the political circumstances of his rise to power here.