He was survived by his wife, Margaret (1725 – 14 July 1807), to whom he was married for over 50 years.
In 1768 Gilpin published his popular Essay on Prints where he defined the picturesque as '"that kind of beauty which is agreeable in a picture" and began to expound his "principles of picturesque beauty", based largely on his knowledge of landscape painting.
Even more unusually, he expressed ideas about the perception of beauty which were purely aesthetic and often divorced from other qualities of the object viewed, such as morality or utility.
After working as curate, Gilpin became master, and from 1755 headmaster, at Cheam School.
Some extra help from the artist, perhaps in the form of a carefully placed tree, was usually required.
In contrast to other contemporary travel writers, such as Thomas Pennant, Gilpin included little history, and few facts or anecdotes.While there he took as a child pupil the future poet Caroline Anne Bowles.Another pupil was his nephew, the painter William Sawrey Gilpin.In 1782, at the instigation of Mason, Gilpin published Observations on the River Wye and several parts of South Wales, etc.relative chiefly to Picturesque Beauty; made in the summer of the year 1770 (London 1782).Even Gilpin's descriptions can seem quite vague, concentrating on how scenery conformed to picturesque principles rather than its specific character.In one much-quoted passage, Gilpin takes things to an extreme, suggesting that "a mallet judiciously used" might render the insufficiently ruinous gable of Tintern Abbey more picturesque.(Elizabeth Bennet, in Pride and Prejudice, notably refuses to join Mr.Darcy and the Bingley sisters in a stroll with the teasing observation, "You are charmingly group'd, and...This was illustrated with plates based on Gilpin's sketches, etched by his nephew William Sawrey Gilpin using the newly invented aquatint process.There followed Observations on the Lake District and the West of England and, after his move to Boldre Remarks on Forest Scenery, and other woodland Views... Gilpin's watercolour technique has been compared to that of Alexander Cozens.