The Union Offices were designed by Oamaru architects and civil engineers Brinsley and Stewart, and built for commission agent William Aitken in 1877. Sitting on Tyne Street it is an integral part of the outstanding Victorian streetscape for which the Harbour/Tyne Street Historic Area (Register No. 7064) is known.

The land on which the Offices were built was leased to William Aitken in 1874. In 1877 Aitken built a suite of offices, known as the ‘Union Offices’ (shown in relief on parapet on Tyne Street). From an article in the North Otago Times on the building’s completion, it would seem that these offices were intended as rental office accommodation, as they were noted as being in the business portion of Oamaru and therefore ‘certain to command good rents.’ Little further is known about William Aitken.

The building was designed by Brinsley and Stewart (who then took offices there). The stonemasons were Barclay and Kay, and the carpenter was John Bain. The Union Offices added ‘one more link to the handsome and substantial chain of stores and offices which now encircles the Harbor [sic] Board Block.’

The North Otago Times described the building as in the ‘Corinthian style’: ‘on the front of the ground floor are square columns, with carved capitals and cornice, and on the upper storey, three-quarter round columns and capitals, and medallion cornice.’ The Union Offices has a frontage to Harbour Street of over 22 ft. (6.7m). It was divided into five offices, ‘all well lighted and properly finished.’ Two offices were located on the ground floor, while three were upstairs, two facing Tyne Street, and one to Harbour Street.

In 1880 Aitken transferred the lease to James Cobden. The mortgagor called in the loan in 1883 and the lease was transferred to James Hassell. Hassell died shortly afterwards and in 1884 the lease was transferred to The Commercial Property and Finance Company. Street directory information indicates that the building was probably sublet to a number of tenants in the late nineteenth and early twentieth centuries. The tenants were professionals including Joseph Mirams (barrister and solicitor) with partner John Newton (who occupied the building from the late 1870s to the late 1890s), commission agent John Church, and civil engineers Norman Kirkcaldy and Percy Mitchell. The Commercial Property and Finance Company transferred the lease to grain and seed merchant Charles Wilkinson Cooke in 1903.

The Oamaru Mail Company took over the lease in 1916, occupying the building till the end of the 1960s. The Oamaru Mail Company had taken over the adjoining Smith’s Grain Store in 1906. George Jones (1844-1920), the editor and owner of the paper, was a prominent figure in Otago, and was Member of the House of Representatives for Waitaki District in the 1880s, as well as being involved in local body politics. At some stage an Oamaru stone addition was made to the Union Offices, extending the premises to the Harbour Street frontage. This addition has steel framed windows, and may be a twentieth century extension.

The Oamaru Licensing Trust took over the building in the early 1970s, and De Geest Joinery in the early 1980s. The Oamaru Whitestone Civic Trust bought the building in the 1990s. Since 1994 the building has been occupied by bookbinder Michael O’Brien, who continues to run his book binding business from the Union Offices in 2008. The Union Offices are an integral part of the outstanding Victorian streetscape of the Harbour/Tyne Street historic area in Oamaru.