On May 22, 1937 the West indies Sugar Co. Ltd. (WISCo) was founded as a subsidiary of sugar industry refiner Tate & Lyle with a capital of £600,000.  That same month WISCo purchased 17 plantations in the Parish of Westmoreland and eight in Clarendon, several formerly owned by James Charley, John Charley and the Morris family.  The purchase included sufficient acreage but the sugar factories were old and small.  It was decided to build a new central sugar mill in Frome to replace the seven small sugar factories, construction of the new sugar mill was finished in 1938.​

On November, 1937 WISCo acquired Monymusk from United Fruit Co. who since 1901 was involved in the sugar industry in Cuba and since the late 1920s also owned Bernard Lodge and Amity Hall sugar factories in Jamaica.  Construction of the new Monymusk central sugar mill was postponed due to WWII but was finally completed in 1949 after the acquisition of the neighboring Blog Plantation, making Monymusk the second largest sugar factory in Jamaica behind Frome.  Production at Monymusk increased from 16,000 mt in 1938 to 80,600 mt in 1965.  Under WISCO management, its sugar mills had higher productivity than the average of the trade.

As a result of the 2009 Government privatization of the sugar industry efforts, in 2011 Monumusk was awarded to Pan Caribbean Sugar Co., the subsidiary of Chinese-based Hua Lien International Holding Co. Ltd. that operates six sugar mills in Africa.  ​Although Monymusk had a production capacity of 65,000 mt., sugar production at Monymusk for the 2016/17 and 2017/18 crop years was only 11,200 and 8,100 mt.  ​Due low production and heavy losses as a consequence, Pan Caribbean decided to cease to operate Monymusk and returned it to the Government after the 2018 crop year.

​Very near Monymusk sugar mill is the modern Clarendon Distillery where Monymusk Rum is produced since 2012.  Molasses for the distillery were produced by Monymusk sugar mill until it closed down.  Clarendon Distillery is owned by National Rums of Jamaica Ltd.(NRJ) which is a conortium between the Government of Jamaica, Demerara Distillers Ltd. of Guyana and Maison Ferrand of France who own 73% and Diageo who owns the remaining 27%.

Why Diageo, the big British conglomerate is involved in this enterprise?  Well, it is all because of Henry Morgan, the Port Royal buccaneer also known as Captain Morgan.  Diageo produces Captain Morgan Spiced Rum for the US market at a large distillery in St. Croix, USVI due to the tax advantages for rums produced in a US Territory.  Since there is no tax benefits for rum exported to the European Union for rums from the USVI, the Captain Morgan Spiced Rum sold there is produced at Clarendon Distillery.  As an additional curious note, since Diageo does not own the rights for the name in jamaica, Captain Morgan Spiced Rum sold in Jamaica is produced by J Wray & Nephew.