Each year the Athenians elected ten archons from among the rich and noble, and at the end of that year the ten graduated into the Areopagus, where they served for life. […¶] In the year 487/6, however, a new law provided that the archons should be chosen by a procedure ending in a lottery. Henceforth, these officials would be selected by chance and not because of their special qualities of lineage, mind, or character. […¶…] Aristotle reports that “After the Persian Wars the Council of the Areopagus grew strong again and controlled the city . . . . For seventeen years the constitution remained the same, with the Areopagites in charge.” (Aristotle, Ath.Pol. 23.1; 25.1) These seventeen years (479 – 462) were the period when Cimon came to exercise the dominant position in Athens. Right after the Persian War, most Areopagites had still been elected rather than allotted, and their prestige had been enhanced by their good service in the war. They passed no new laws: they merely began to exercise their old informal rights, shielded by a favorable political climate, especially the support of the increasingly popular Cimon.
Source: wiktionary