The National Trust took over the management of the Glyderau and the Carneddau in 1951 in lieu of death duties on the Penrhyn Estate. The total area is about 7,000 hectares, half of which is common land with registered grazing rights for 45,000 sheep and 741 ponies. There are eight tenanted farms on the estate and the National Trust is responsible for the maintenance of footpaths and drystone walls, some of which date back many hundreds of years. The two mountain ranges form part of the Snowdonia National Park.