The League was the earliest and the longest lasting of all known Greek alliances. Despite its name it included all of Sparta's allies and not only Peloponnesian cities.
Bouchard, Elsa. "Formation of the Peloponnesian League". The Literary Encyclopedia. First published 01 March 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=11179, accessed 19 April 2014.]