The Alcmaeonid clan were one of the wealthiest and most politically important in Athens; a kind of Classical Greek equivalent to the Kennedys in the US.

As well as Cleisthenes, who took power in Athens in 510 BC and again in 507 BC, their famous sons included Pericles, who dominated Athenian politics at its highest point between 450 and 429 BC, and Cleisthenes' grandfather and namesake Cleisthenes tyrant of Sicyon.

According to Herodotus (Book 6, verse 125) it was Alcmaeon, great-grandfather of Cleisthenes of Athens, who had made the family rich. He did so by giving all the assistance in his power to a group of Lydians seeking passage to the Oracle at Delphi. When the Lydians returned to their king, Croesus, he invited Alcmaeon to his capital at Sardis to reward him; inviting him to take as much gold as he could carry from his treasury. The canny Alcmaeon took advantage of the situation by wearing baggy clothes and wide-topped boots and filling every crease of clothing, as well as his hair and mouth, with gold dust. Scarcely able to walk for the weight of gold, Croesus burst out laughing at Alcmaeon's bulging cheeks and swollen figure and gave him all the gold he was carrying and as much again. Suddenly rich, Alcmaeon was able to keep race-horses with which he won the chariot race at the Olympics.

It is from Croesus's legendary wealth that we get the expression 'rich as Croesus'.