Nailsea's early economy relied on coal mining, which began as early as the 16th century. The earliest recorded date for coal mining in Nailsea was 1507 when coal was being transported to light fires at Yatton. By the late 1700s the town had a large number of pits. Around this time Nailsea was visited by the social reformer Hannah More who founded a Sunday school for the workers. The Elms Colliery,(Middle Engine Pit), one of the most complete examples of an 18th-century colliery left in England, is now in disrepair. It has been designated a Scheduled Ancient Monument and is included in the Heritage at Risk Register produced by English Heritage. Remains of the old pits, most of which had closed down by the late 19th century as mining capital migrated to the richer seams of South Wales, are still visible around the town.