Argos was already ancient when the surviving Greek accounts of its kings were written. Archaeological investigation of the Aspis hill has revealed an early settlement history, but not the unbroken occupation from around 5000 BCE claimed in some popular retellings. The published excavation identifies a brief settlement near the end of the fourth millennium BCE, substantial occupation in the Middle Helladic period during the first half of the second millennium BCE, and later episodes of use. The different phases matter: the antiquity of a place does not by itself prove continuous habitation on every part of the site. In the heroic geography of the Iliad, Argos belongs to the territory led by Diomedes, alongside other communities of the Argolid. The poem preserves a legendary picture of the region, while excavation provides a separate account of its material past.

The founder in Argive tradition was Phoroneus, the son of the river god Inachus and the nymph Melia. Pausanias records that he first brought people together into a community, which was called the city of Phoroneus. Traditions also connected him with the introduction of fire and the worship of Hera. His daughter Niobe was remembered as an early mortal companion of Zeus, and their son Argus became the king whose name was given to Argos and, in some ancient accounts, to the wider Peloponnese. Apollodorus distinguishes this king from the later Argus Panoptes, the many-eyed guardian appointed by Hera to watch over Io. The giant belongs to the story in which Hermes kills the watcher and releases the transformed maiden; he should not be substituted for the city's royal namesake. These linked genealogies gave the Argive landscape an ancestry, connecting its river, its first community and its rulers to the gods.

The succession after Phoroneus is preserved in genealogies whose details vary between writers. Names such as Criasus, Phorbas, Triopas, Iasus, Crotopus and Gelanor connect the early rulers to the arrival of Danaus, the prince who fled from Egypt with his fifty daughters. Pausanias tells how Danaus and Gelanor put their rival claims before the Argives, who postponed their decision. At dawn a wolf attacked and defeated a bull outside the city, and the people interpreted the omen in favour of the newcomer. Danaus received the kingdom, and the inhabitants were called Danaans after him. The marriage of his daughters to the fifty sons of Aegyptus then brought catastrophe. Forty-nine brides killed their husbands at their father's command; Hypermnestra alone spared hers. This husband was Lynceus, son of Aegyptus, not the Messenian Argonaut of the same name. Their son Abas continued the Argive royal line. Pausanias places the husbands' heads at Larisa and their bodies at Lerna, distinguishing the two burial locations.

Among the descendants of Abas were the rival twins Acrisius and Proetus. Their conflict divided the royal territory, with Acrisius ruling Argos and Proetus associated with Tiryns. Acrisius was warned that a son of his daughter Danae would kill him, so he shut her in a bronze chamber. The tower of later art and retelling should be distinguished from the underground enclosure described by Apollodorus. Zeus nevertheless reached her in the form of a shower of gold, and she bore Perseus. Acrisius set mother and child adrift in a chest, but they survived and reached Seriphos. Perseus eventually killed the Gorgon Medusa and returned towards his ancestral kingdom. The prophecy was fulfilled not in a deliberate attack on Acrisius but through a discus thrown at games in Larisa in Thessaly. The discus struck the old king and killed him. In the succession story, Perseus then exchanged kingdoms with Megapenthes, the son of Proetus, and was credited with founding Mycenae. This is a legendary explanation of relationships between Argive cities, not a dated archaeological account of a transfer of power.

In the historical period, Argos was a major Peloponnesian city with its own political institutions, sanctuaries and territorial interests. Pheidon, a ruler whose precise date remains disputed, was credited by Herodotus with establishing measures used in the Peloponnese and with intervening in the Olympic Games. The city was closely connected with Hera, whose great sanctuary, the Heraion, stood outside Argos rather than being another name for the city itself. Pausanias describes the goddess's gold-and-ivory image by Polykleitos and the surrounding sacred landscape. Argos and Sparta repeatedly contested regional power and territory, including the district of Thyreatis remembered in Herodotus's account of the battle of champions. Herodotus also preserves differing explanations of Argos's decision not to join the Greek alliance against the Persian invasion. These disputes belong to a history more complex than a simple contrast between two unchanging enemies. The city continued through the Hellenistic and Roman periods, and its surviving monuments sit alongside the much older stories of founders, royal houses and divine patrons.