Passage 5.8.6
δῆλον δέ· ἐξ οὗ γὰρ τὸ συνεχὲς ταῖς μνήμαις ἐπὶ ταῖς Ὀλυμπιάσιν ἐστί, δρόμου μὲν ἆθλα ἐτέθη πρῶτον, καὶ Ἠλεῖος Κόροιβος ἐνίκα· εἰκὼν μὲν δὴ οὐκ ἔστιν ἐν Ὀλυμπίᾳ τοῦ Κοροίβου, τάφος δὲ ἐπὶ τοῖς πέρασι τῆς Ἠλείας. Ὀλυμπιάδι δὲ ὕστερον τετάρτῃ καὶ δεκάτῃ προσετέθη σφίσι δίαυλος· Ὕπηνος δὲ ἀνὴρ Πισαῖος ἀνείλετο ἐπὶ τῷ διαύλῳ τὸν κότινον, τῇ δὲ ἑξῆς ἐπὶ τῷ δολίχῳ Ἄκανθος Λακεδαιμόνιος .
The evidence for this is quite clear. For from the time when the continuous records of the Olympiads began, the first competitions held were those in running, and the Elean Coroebus was victorious. There is indeed no statue of Coroebus at Olympia, but his tomb is at the boundaries of Elis. At the fourteenth Olympiad after this, the double-stadion race was added, and Hypenos of Pisa won the olive wreath in the double-stadion. In the Olympiad immediately thereafter, Acanthus of Sparta won the dolichos race.