The Clan Line was founded in 1877 in Liverpool as C. W. Cayzer & Company, trading from the UK to India. The company became Cayzer, Irvine & Company in 1878 when Captain William Irvine joined the firm. In 1881 the Clan Line Association of Steamers was formed and, with an influential Glasgow businessman joining the firm, the company was moved to Glasgow. Clan Line head office was established at 109 Hope Street, Glasgow. New ships were built and managed for the Association by Cayzer Irvine, with Cayzer retaining ownership of the original six Clan ships.
In 1890 the name of the company became The Clan Line of Steamers Limited with Cayzer holding majority interest. The company purchased the Persian Gulf Steam Ship Company in 1894 and their fleet of four ships. Fare at this time from Liverpool to Madras or Calcutta was ?45 first class and ?30 second class.
The company became Cayzer, Irvine & Company, Limited, in 1907 and in 1918 the assets of the Scottish Shire Line were acquired. The same year the Houston Line was taken over together with the British and South American Steam Navigation Company, but all three of these companies retained their own system of ship naming, colours and liveries.