The Leeds Mercury was established by John Hirst in 1718 as a weekly newspaper in the rapidly growing West Yorkshire woollen textile town. The Mercury was one of the foremost provincial newspapers, publishing articles by many distinguished writers and gaining a reputation as a leading reporter of Liberal politics.

In 1801 the Mercury was purchased by Edward Baines, a young Liberal and Nonconformist printer, who used the newspaper to campaign tirelessly for moderate social and political reform. His son, Edward, worked as a journalist for the newspaper, and became proprietor following his father's death in 1845. He in turn left the controlling share in the newspaper to his children in 1890.

The Mercury began as a four-page Saturday newspaper, but it gradually increased in size, frequency and popularity, being published daily from 1861. By 1900 week-day editions contained ten pages, but on Saturdays it included twelve pages and an additional supplement, all priced at only 1d. The circulation also expanded to more than 5,000 copies per week by the 1820s, and the Mercury claimed in the edition of 4 January 1840 to have eight times the 'average circulation of Provincial Papers'.

The diversity of articles in the Mercury was crucial to its popularity. As a local newspaper, it included unusually extensive coverage of parliamentary and national affairs. This particularly flourished under the editorship of Thomas Wemyss Reid, who established a London Office in 1870 and who gained the confidence of Prime Minister William Gladstone. However, local news remained central to the paper, with detailed articles on government and civic events in Leeds and surrounding Yorkshire towns. Simultaneously, the Saturday paper became a self-styled 'first class general and family newspaper', with many articles catering to specialist interests and offering general family entertainment.