As a settlement, Kilmun is substantially older than most of its neighbours (see Parish Church below). Like them, it developed as a watering-place (a pleasure resort/spa) for Glasgow merchants after 1827, when a quay was built by the marine engineer David Napier. It was a regular stop for the Clyde steamer services until its closure in 1971.
Kilmun is also home to an extensive arboretum managed by the Forestry Commission. Established in the 1930s to monitor the success of a variety of exotic tree species in the humid west coast environment, it includes specimens of Sequoia, Japanese Larch, Araucaria araucana (monkey puzzle) and Japanese Chestnut amongst many others from around the world. A series of woodland walks have been established of varying gradients and degrees of difficulty, which link by a forestry track to Benmore wood at the top of Puck's Glen.