One towards the East, i.e. towards Megara, reading: "Here is not Peloponnesus, but Ionia" (τάδ᾽ οὐχὶ Πελοπόννησος, ἀλλ᾽ Ἰωνία) and the one towards the West, i.e. towards the Peloponnese: "Here is Peloponnesus, not Ionia" (τάδ᾽ ἐστὶ Πελοπόννησος, οὐκ Ἰωνία); Plutarch ascribed the erection of the stele to the Attic hero Theseus, on his way to Athens.

Since 1893 the Corinth Canal has run through the 6.3 km (3.9 mi) wide isthmus, effectively making the Peloponnese an island.

He abandoned the project owing to technical difficulties, and instead constructed a simpler and less costly overland stone ramp, named Diolkos, as a portage road.

Julius Caesar foresaw the advantages of a link for his newly built Colonia Laus Iulia Corinthiensis.

In the modern era, the idea was first seriously proposed in 1830, soon after Greece's independence from the Ottoman Empire, and was brought to completion in 1893 after eleven years' work.