Map of Södermanland, 18th century

This historical map of Södermanland, also known as Sörmland, was published towards the end of the 18th century by the surveyor E. Geringius at Lantmäteriet. The name means Södermännens land, which was the name of the people who lived in the "land south of Lake Mälaren". It is a land rich in stones, burial mounds and other ancient monuments. There are about 300 rune stones in the region, only Uppland has more. The oldest stone at Skåäng near Vagnhärad bears an inscription with older runes from the 5th or 6th century. From Sörmland we also have a rune stone in Aspa with the oldest indigenous evidence of the name Svitjodwhich our ancestors called their country long ago.

The oldest archaeological traces of the ancestors of the southerners are about fifty settlements from the Early Stone Age. From this period, 8000-6000 years ago, a number of stone axes have been found, known as Lihultyxor. When the population settled down and became permanent farmers, they began to import fine flint trousers from Skåne or Denmark. From the Neolithic period, a rich variety of finds have been made.

Several finds have also been made from the Bronze Age, and the archaeologists have concluded that the central sites of the Bronze Age culture were in Rekarne, a historic settlement in northwestern Södermanland that roughly corresponds to today's Eskilstuna municipality, and at Lake Yngaren, a lake 15 kilometres northwest of Nyköping, among other places.

From the migration period during the 400s and 500s, many gold finds have been made in Södermanland, including Sweden's largest known gold find, made in 1774 at The Tureholm Estate. The gold, which weighed more than 12 kg, is believed to have come from Germanic warfare with the Roman Empire. Also from the Migration period is Uppsa Hill, one of the country's largest and the region's largest royal mound.

Södermanland has seen much blood and suffering over the centuries. The Middle Ages were no exception, and much of the fighting of the Union period took place in Södermanland.