By the mid-eighteenth century the need to provide accommodation for the Public Records of Scotland was widely recognised. They had been kept for many years in 'two laigh rooms under the Inner Session House in a perishing condition’, and a proper home for them had been proposed as early as 1722. In 1752, an Act that led to the building of the Royal Exchange gave Commissioners power to build a register house. Nothing came of these proposals until 1765, when representations to the Government resulted in a grant of £12,000 being made for the construction of a ‘proper repository'. The Earl of Morton, the Lord Clerk Register, in association with the architect, Robert Baldwin, published a design in 1767 that consisted of a single storey square building with a central dome, however, there was disagreement over the site. The Earl of Morton had suggested a site to the south of the city at Heriot's Hospital, which was considered too distant from the law courts by members of the legal profession and a delay followed. In 1769, the City supplied the ground opposite the north end of the newly completed North Bridge, where a significant public building was likely to encourage the development of James Craig’s design for the New Town. It was a prestigious site facing along one of the principal street vistas in Edinburgh, standing at the meeting place of the Old and New Towns, and visually terminating the first major route between them.

In 1761, Robert Adam and William Chambers, were jointly appointed "Architects of the King’s Works", with Adam having specific responsibility for Scotland. Adam resigned from this post in 1768, on his election as an MP, prior to receiving any commissions for a major public building. William Chambers was to go on to receive the major public commission for the design of Somerset House in 1776. Before that, in September 1769, Robert Adam, along with his brother James, had received the commission for the design of Register House. The then Lord Clerk Register, Lord Frederick Campbell, was a friend of Robert Adam who had worked on alterations to Campbell's house at Ardincaple, Dunbartonshire, and other Trustees were patrons or supporters of Adam. The commission gave Adam the opportunity to design a monumental public building of national importance.

Adam's design of 1771 comprised a two storey and basement building forming a rectangular quadrangle (200 by 155 ft {61 by 47 m}) with towers projecting at each corner and half way along each of the short sides, with the courtyard filled by a central hall under a domed rotunda surrounded by a ring of offices. A number of sources can be seen as probable inspiration in the preparation of the design. The dome of the Pantheon being the clearest influence from antiquity. There are also parallels between Adam's scheme and the earlier plans by Lord Morton and Robert Baldwin for a single storey building on the site, although much more is owed to Adam's own proposals for Syon House from 1761. The rotunda at Register House playing a similar role to his unexecuted plans for a domed saloon infilling the central courtyard at Syon.

Work on the new building began in 1773 with the digging of the foundations. However, the scheme was reduced on financial grounds, and when the foundation stone was laid in 1774 only the south range, rotunda and the front half of the east and west ranges from the 1771 scheme were proposed for immediate construction. The building was, however, built to allow for its extension to the original dimensions if additional funding became available. 

The structure is almost entirely of either stone (from the local Craigleith and Ravelston quarries) or brick making the building fireproof and providing stability for the storage of heavy record volumes.  This meant that the building was expensive and, despite its less elaborate form and restrained decoration, the money made available was insufficient even to allow construction of Adam’s reduced design.  Work was suspended at the end of 1778 and the roofless shell of the building stood empty as "the most expensive pigeon house in Europe."  In 1785, a further government grant allowed work to recommence, with the building being ready for occupation by the end of 1788.

Adam was based in London during the time he spent working on Register House and made only rare visits to inspect the work in progress. Conduct of the undertaking from London does not seem to have reduced his impact on the design and construction. He insisted on a high standard of workmanship at all times and sent some of the materials from London, such as the Liardet stucco for the external decoration. Adam also insisted that there should be no building during the winter to allow the building materials to settle and consolidate. Day to day supervision of the work on site was left to James Salisbury, the clerk of works, who had been personally recommended to the Trustees by Adam.  John Adam, who lived in Edinburgh, visited the work from time to time, and the Adam office produced a steady stream of large-scale drawings of details throughout the course of the work.

The building is 2-storey on a raised basement forming a quadrangle with a domed circular reading room in the centre of court. It is finished in a polished cream sandstone ashlar with projecting taller single bay pavilions at the corners and centre of the side elevations. The towers at each end of the façade are crowned with turrets and cupolas, project from the main wall-plane and are emphasised by the Corinthian columns on their upper storeys. The ground floor and pavilions are arcaded with windows set in arches. The main south elevation has rusticated stonework at the ground floor and a Corinthian centrepiece with a pediment bearing the roundel of the Royal Arms in patent stucco. The advanced pavilions have a pair of Corinthian columns at first floor framing Venetian windows set in recessed arches.

The basic structure is Palladian, a piano nobile over rusticated arches, but encompassing the spirit of the neo-classical. The overall elegance of the frontage relies on proportion and the contrast between vertical and horizontal elements, rather than decorative elaboration to provide the 'movement' which Adam aspired to for the exteriors of his buildings.

The interior was very simply finished except for the massive rotunda that is the highest built to Adam’s designs and is architecturally the most important room in the whole building. It forms a ‘magnificent Roman space’, 70ft (21 m.) high from floor to oculus and 5 ft (15 m.) in diameter. It is surrounded by bookcases set into the arcaded walls of the drum, circled by a gallery at first-floor level and with the dome divided into eight segments, each containing a plaster roundel. It retains Adam’s decorative scheme. The plasterwork in the dome was carried out by Thomas Clayton of Edinburgh, except for the eight bas-relief roundels, which were produced in London to Adam’s direction.

Robert Adam died suddenly in 1792 before the building was complete. By the start of the Napoleonic war in 1803 the completed section had cost £31,000, but by its end it the accommodation was already recognised as inadequate. In 1822 the building was enlarged to the dimension of Adam’s 1771 design, under the architect Robert Reid.  Reid largely followed Adam's intentions, completing the side facades to Adam’s designs, but instead of building the new north elevation to match Adam’s south facade, which Adam intended, he substituted a design based on the side elevations.  In 1790 a clock was installed in the south-east tower and a wind-vane in the south-west, both supplied by the London clockmaker Vulliamy. David Bryce pushed back the front area wall in 1849, in order to accommodate the statue of Wellington and this process continued with the wall being pushed back further and the squaring-off of the staircase in 1890. Further buildings have been added behind Adam’s original one, but the latter remains as the public face of the complex, facing out onto Princes Street and forming the first purpose built record offices in Britain and one of the oldest archive buildings still in continuous use in the world.

JK GILLON