The medieval coastal road from Turku to Vyborg was originally just a riding track used mostly by envoys of the Swedish king. In the 15th century the road followed an established route from Turku via Kaarina, Piikkiö, Paimio and Halikko to the medieval marketplace of Salo. The road then continued via Perniö and Tenhola to the coast, and then via Pohja to Karis, where the road branched into a southern and a northern route. The south road went via Raasepori and Ingå to Pikkala, joining with the northern route via Lohja, Virkkala and Siuntio. From Pikkala the road continued via Kirkkonummi and Espoo to the parish village of Helsinki. Before the town of Helsinki was founded in 1550 the road went via Sipoo to Porvoo, which became a town in about 1380. The road continued to Pernå and Degerby, which became the town of Loviisa in 1752. Finally the road went on via Pyhtää, Vehkalahti, Virolahti, Virojoki and Säkkijärvi to Vyborg. With the stagecoach decree of 1633, rested horses were available about every 20 kilometres and the journey could be made in a week.

The Great Northern War of 1721 cut off the route to Vyborg and the road only went as far as Hamina, which had been founded at Vehkalahti. The route was re-opened after the Treaty of Åbo (Turku) of 1743, but now beyond the crossing point at Ahvenkoski on the Kymijoki River was Russian territory. But now the road extended to St. Petersburg.

When Finland became an autonomous grand duchy in 1809, the coastal road became focused on the Helsinki-St. Petersburg stretch. When territory was ceded after the Second World War, the lower Vyborg road lost its main road status. In many places the old route runs alongside the present King's Road, which has been straightened over the decades.