Since the rise of seaside resorts with the arrival of the railways in the 19th century, Devon's economy has been heavily reliant on tourism. The county's economy has followed the declining trend of British seaside resorts since the mid 20th century, with some recent revival. This revival has been aided by the designation of much of Devon's countryside and coastline as the Dartmoor and Exmoor national parks, and the Jurassic Coast and Cornwall and West Devon Mining Landscape World Heritage Sites. In 2004 the county's tourist revenue was £1.2 billion.