The finds were made by teams working on the £17 million A75 Dunragit bypass in Wigtownshire.
Tools, arrowheads, urns and bead necklaces from the Mesolithic (9000 BC to 4500 BC), Neolithic (4500 BC to 2000 BC), Bronze (2500 BC to 800BC) and Iron Ages (800 BC to 500 AD) were found, along with the Iron Age village and a Bronze Age cemetery.
A 130-piece jet bead necklace was of particular interest to archaeologists, who were able to trace its origin to Whitby, North Yorkshire, around 155 miles from where it was found.
The discoveries were showcased as work on the new road was completed, and they have been described as "very exciting" by Historic Scotland.
Scottish Transport Minister Keith Brown viewed the artefacts in Edinburgh, and said: "The finds at Dunragit, which would have remained uncovered had the new bypass not been built, are truly stunning and underline the importance of the value we place on meeting our environmental obligations as we plan and construct essential new infrastructure.
"The concentration of artefacts from the Mesolithic to post-medieval periods was highly unexpected, but gives an invaluable insight into the land use and settlement of south-west Scotland over the past 9000 years. The necklaces are of particular interest because they are the first to be uncovered in the south west of Scotland."
A decision is still to be made on where the collections will be stored or displayed.
Rod McCullagh, senior archaeology manager at Historic Scotland, said: "The bypass has been constructed while successfully avoiding the known archaeology, and an unforeseen wealth of archaeological information has been recovered.
"These are exciting discoveries which offer a rich understanding of the settlement of south-west Scotland over the past 9000 years."