An organisation which holds more than 15 million drawings, photographs and manuscripts will formally merge with Historic Scotland on Thursday.
Edinburgh-based Royal Commission on the Ancient and Historical Monuments of Scotland (RCAHMS) was set up in 1908.
The Queen, whose great grandfather Edward VII established the body, has been sent its final report, which gives a history of its work.
RCAHMS will become part of new body Historic Environment Scotland.
Historic Scotland manages sites across Scotland including Edinburgh Castle, Stirling Castle, Skara Brae in Orkney, Linlithgow Palace and Urquhart Castle on the banks of Loch Ness.
Historic Environment Scotland was established by the Historic Environment Scotland Act 2014.
RCAHMS' first report involved a survey of Habchester fort in the Scottish Borders.
Since 1908, it has gone on to record thousands of historic places and produce hundreds of books and reports.
In recent years, the commission has documented the remains of a Viking shipyard on Skye, historical sites on St Kilda and taken thousands of images of the Scottish cemetery in Calcutta, India.
RCAHMS also holds one of the largest and collections of aerial imagery in the world.
Among the tens of millions of images there are 1.6 million of Scotland, including some of the earliest aerial photographs ever taken of the country.
In its final report, RCAHMS addresses the Queen.
It said: "Our work has always been driven by an idea - in its simplest form, that the built and historic environment of Scotland must be recorded and researched to ensure that its exceptional cultural value is understood and protected by current and future generations.
"This report, our last as a Royal Commission, documents how we have pursued this idea for over a century."