Alloa Brewer James Maclay (1801-1875) worked at the Old Devon Ironworks in Tillicoultry in the late 18th century, later as an accountant at the Hutton Park Brewery in Alloa. In 1830 he acquired the lease to the Mills Brewery in the town, where he founded the brewery as James Maclay, Ale, Porter, Table and India Beer Brewer of Alloa. James Maclay established himself as a brewer of great repute over the next 39 years and in 1870, James built the Thistle Brewery at East Vennel, Alloa, in anticipation of the ending of his lease on the Mills Brewery. He moved into the brewery in November 1875, which became the home of Maclays Alloa Ales until 1999.
James Maclay died in December 1875, leaving his two sons James and John to run the company, now renamed J&J Maclay. Robert and John Ramsay, two brothers who ran a bottling business in Dunfermline, acquired the Thistle Brewery and associated maltings following the dissolution of the partnership of J. & J. Maclay in 1881. The business then traded under the name Maclay & Co, and from 1896 as Maclay & Co Ltd. In 1888 two new partners, Alexander Fraser and James Drummond, were assumed, and the following year the Ramsay brothers sold them their interest in the company.
Maclays ales won medals at Vienna in 1894 (Oatmeal Stout), Newcastle in 1898 and Paris in 1900.
In 1910 parts of the brewery were damaged by a fire in which much of the company's archive was destroyed. The firm was unable to recommence brewing for nearly a year.
Maclays acquired part of their old home, the Mills Brewery in Alloa from Robert Henderson & Co Ltd in 1948, This company had operated in the Mills Brewery since Maclay's lease had expired back in 1871.
Despite the renown of their Oat Malt Stout, the change in fashion away from dark beers led to difficulties for the company in the 1990's and brewing at the Thistle Brewery ceased in 1999. In 2001 the company ceased using the buildings as their office base. The Thistle brewery has since been demolished and replaced by retail units and flats. Only part of the brewery survives and is now a pub called The Old Brewery, owned by Dunbar based Belhaven.
On March 10, 1994, the company changed its name to Maclay Inns Limited to better reflect its current business model. The company acquired the Clockwork Beer Company in Glasgow, which operated as the Maclays brewery under the Three Thistles PLC, brewing its own range of beers and Maclays recipes.
In 2012 Tennent Caledonian acquired a substantial minority shareholding.
On 23rd January 2015 it was announced that the company had gone into administration. In June 2015 it was reported that Stonegate Pub Company had bought the remaining Maclays owned pubs from administration.
Maclays beers are brewed under licence by Belhaven Brewery (owned by Suffolk based Greene King PLC) and by Sleeman Breweries in Canada.