The shift from one role to the other is itself a kind of compressed history, but the building's origins are stranger still: it began as a perk of the job, obtained by a man who used his position as the park's own bailiff to secure himself a slice of the park.

The house stands on the site of a Bailiff's Lodge that probably dates to the 17th century. The building as it exists today was originally constructed in 1776 by Sir John Blaquiere, a Member of Parliament who served as Secretary to the Lord Lieutenant and was, according to architectural historian Mark Bence-Jones writing in 1988, one of the leading figures in the political life of Ireland during the later 18th century. Blaquiere obtained his demesne within Phoenix Park on the basis of his role as the park's bailiff, a position of custodianship he used to considerable personal advantage. By 1782, he was asked to surrender the house and grounds in exchange for compensation, and the property passed into official use as the residence of the Chief Secretary, the principal executive officer of Irish government under British rule. The house was modified repeatedly over the following decades. In 1832, Lord Naas, later the 6th Earl of Mayo and Viceroy of India, added a large glass conservatory while serving as Chief Secretary. Around 1865, during the tenure of Chichester Fortescue, later Lord Carlingford, the two bowed projections at either end of the principal front were connected by a single-storey corridor, deepening the central rooms considerably, with the main wall carried on Ionic columns. The result is a predominantly late Georgian house of two storeys, with an enfilade of reception rooms running along the garden front. In 1927, the property became the United States Legation, and subsequently the Embassy.

The building sits within Phoenix Park, which is freely accessible to the public, though the Ambassador's residence itself is not open for casual visits. The exterior and grounds can be viewed from within the park, and the surrounding landscape retains something of the demesne character that Blaquiere originally engineered for himself. Those who know what they are looking at will notice the telltale bowed ends of the facade and the low corridor linking them, the accumulated result of two centuries of pragmatic alteration by some of the most powerful administrators in Irish colonial history.