Classical liberalism is a political ideology and a branch of liberalism that advocates civil liberties under the rule of law with an emphasis on economic freedom. Closely related to economic liberalism, it developed in the early 19th century, building on ideas from the previous century as a response to urbanization and to the Industrial Revolution in Europe and North America. As a term, classical liberalism was applied in retrospect to distinguish earlier 19th-century liberalism from social liberalism.