William McDowall of Garthland (1749-1810) was a politician and merchant of the West Indies. He was the son of William McDowall and Elizabeth Graham and heir to a large commercial empire in the sugar, rum and slave trade, including estates in the West Indies in Grenada and St Kitts, as well as extensive land across Scotland. He was educated at the University of Glasgow and was admitted advocate in 1771. He sat as MP for Renfrewshire in 1783-86, Ayrshire in 1789-90, Glasgow Burghs in 1790-1802 and Renfrewshire again in 1802-10. He supported the Pitt administration and was ‘adverse’ to the abolition of the slave trade. He was a partner in the firm Alexander Houston & Co., a major trading firm in the West Indies set up in 1776, which ultimately failed in 1801. Following from this, he faced financial difficulty towards the end of his life and put his family estate of Castle Semple up for sale in 1808. He died in 1810, unmarried, and was succeeded by his nephew.

The Adam office made designs for additions to the existing Castle Semple for William McDowall in 1791. These included a new range to the front and rear of the house as well as alterations to the interiors of the existing house. Adam visited Castle Semple in both July and September of 1791, however, these proposals were not executed.

Literature:
A.T. Bolton, The Architecture of Robert and James Adam, Volume II, Index, 1922, pp. 6, 79; M. Sanderson, Robert Adam’s Last Visit to Scotland 1791, Architectural History, Volume 25, 1982, pp. 35-46; D. King, The Complete Works of Robert & James Adam and Unbuilt Adam, Volume 2, 2001, p. 161; W. Adams, ‘Classical Paisley’, The Georgian, 2003, pp. 6-8; D. G. Henry & R. G. Thorne, ‘McDowall, William (c.1749-1810) of Castle Semple, Renfrew and Garthland, Wigtown’, The History of Parliament: the House of Commons 1790-1820, 1986, online, [accessed 7 March 2024]; UCL, Legacies of British Slavery Database, online, [accessed 7 March 2024]

Louisa Catt, 2024