The line opened in stages. The section from Ayr to Irvine opened on 5 August 1839. The extension to Kilwinning opened on 23 March 1840 and to Beith on 21 July 1840. The completed line between Ayr and Glasgow opened on 11th August 1840.

Reference: http://en.wikipedia.org/wiki/Glasgow,_Paisley,_Kilmarnock_and_Ayr_Railway (accessed 08Feb21)