During the Peloponnesian Wars, what city states were allied with Athens and who was allied with Sparta?
There is probably no accurate historical record of all of the allied city-states who fought with Sparta and Athens. Nearly all of the city-states (except for Argos and Achaea) on the peninsula of Peloponnese sided with Sparta and its allied Peloponnesian League during the Peloponnesian Wars. The three most powerful were Sparta, Corinth and Thebes; less powerful city-states included Elis, Tegea and Mantinea. Persia later sided with Sparta during the latter stages of the war. Even greater uncertainty surrounds Athens and its allies of the Delian League; members included the Naxians, Catanians, Sicels, Rhegians.
For a complete list of possible Delian League allies, see the link below.
For a comprehensive study of the Peloponnesian League, see the link below.