Threlkeld Quarry, which is situated three miles east of Keswick, originally opened in 1870 to supply railway ballast to the Penrith-Keswick line. Later, the stone was used by the Manchester Corporation Waterworks for their Thirlmere scheme, for railway ballast for the Crewe-Carlisle line, for roadstone, kerbing and for facing buildings with dressed stone. The granite quarry finally closed in 1982 and is now the site for the Threlkeld Quarry & Mining Museum which is run by a group of volunteers.

The extensive quarry site has ample space for the display of the unique collection of vintage excavators and old quarry machinery. The 2ft gauge mineral railway has been relaid and provides a ride into the inner quarry for visitors to view the quarry faces in safety.