Lauriston Castle began as a compact tower house northwest of Edinburgh, built in the late sixteenth century for Sir Archibald Napier of Merchiston. Napier served in royal administration and was the father of John Napier, the mathematician associated with logarithms. The house's defensible form, narrow windows, and stair tower belonged to a Scottish tradition in which landed families combined security with domestic status. Its position above the Firth of Forth connected the estate visually to maritime routes while keeping it within reach of the capital.

Ownership changed repeatedly after the Napiers, and later residents adapted the old tower to new standards of comfort. The most dramatic expansion came in the 1820s for the banker and mineralogist Thomas Allan. Architect William Burn added a substantial range in a picturesque style, integrating the earlier tower into a larger country house. Reception rooms, bedrooms, service spaces, and broad windows transformed the scale and circulation of Lauriston while preserving a deliberately historical silhouette suited to nineteenth-century taste.

In the early twentieth century William Robert Reid and his wife Margaret acquired Lauriston and furnished it as an elegant Edwardian home. Their interiors combined Scottish pieces with Italian furniture, ceramics, textiles, clocks, and decorative arts gathered through dealers and travel. The collections were arranged for domestic enjoyment rather than as a conventional museum display. Gardens and views remained essential to the experience of the house, whose rooms expressed both personal taste and the international collecting habits of prosperous British households before the First World War.

William Reid died in 1919. Margaret continued to live at Lauriston and carefully maintained the rooms they had created together. On her death in 1926 she bequeathed the castle, grounds, and contents to the nation, with the intention that the interior arrangement should remain substantially unchanged. The City of Edinburgh became responsible for the property and opened it to the public. This gift preserved not only individual objects but also their relationships within an inhabited home, giving Lauriston unusual value as a coherent decorative ensemble.

Later stewardship has conserved both the sixteenth-century core and Burn's nineteenth-century additions while protecting the Reid collection. The grounds have acquired further layers, including designed gardens that complement the older landscape without pretending to reproduce every earlier phase. Lauriston Castle now tells a story different from that of a battlefield fortress. Its history concerns professional service, architectural enlargement, private collecting, marriage, memory, and civic inheritance. The survival of furnished rooms allows the changing meaning of a Scottish tower house to be traced from guarded family residence to romantic country house and publicly owned museum.