In the 1770s and 1780s, Johnson expanded his business, publishing important works in medicine and children's literature as well as the popular poetry of William Cowper and Erasmus Darwin.
Pada tahun 1770-an dan 1780-an, ia memperbesar bisnisnya dan menerbitkan karya-karya penting dalam bidang kedokteran, sastra anak-anak, dan puisi karya William Cowper dan Erasmus Darwin.