The Mourne Wall is among the more famous features in the Mournes. It is a 35 km (22 mi) dry-stone wall that crosses fifteen summits, constructed to define the boundaries of the 36 km² (9,000 acre) area of land purchased by the Belfast Water Commissioners in the late 1800s. This followed a number of Acts of Parliament allowing the sale, and the establishment of a water supply from the Mournes to the growing industrial city of Belfast. Construction of the Mourne Wall was started in 1904 and was completed in 1922.
Many of the mountains have names beginning Slieve, from the Irish word sliabh, meaning mountain. As well as many of the well-known mountains such as Slieve Donard, Slieve Lamagan and Slieve Muck, there are a number of other curious names: Pigeon Rock; Buzzard's Roost; Brandy Pad; Percy Bysshe; the Devil's Coach Road; and Pollaphuca, which means "hole of the fairies or sprites".
The Mournes are very popular as a destination for many Duke of Edinburgh's Award expeditions.
The Mountains are said to be C.S Lewis' inspiration for the magical world of Narnia.
Aside from grasses, the most common plants found in the Mournes are heathers. Of these, three species are found: the cross-leaved heath (erica tetralix), the bell heather (erica cinerea), and the ling (calluna vulgaris). Other plants which grow in the area are: Bog Cotton, Roseroot (Rhodiola rosea), Harebell (Campanula rotundifolia), Marsh St John's Wort, Wild Thyme (Thymus serpyllum), Wood sorrel and Heath Spotted Orchids.
Sheep graze high into the mountains, and the range is also home to birds, including the common Raven, Peregrine Falcon, Wren, and Buzzard, and native Meadow Pipit, Grey Wagtail, Stonechat and Snipe. The Golden Eagle, a former inhabitant, has not been seen in the Mournes since 1836.