The archons were the most important officials in Athens after the end of the monarchy. Presumably there was at first one single magistrate elected annually, but by the 6th century BC the college of archons had reached the final number of nine members.
Bouchard, Elsa. "First annual archons in Athens". The Literary Encyclopedia. First published 01 March 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=11146, accessed 21 September 2014.]