Answer: Liberalism
Step-by-step explanation:
Liberalism is the most important ideology born in the 19th century - one that still drives politics and economics in many countries today.
Liberalism is the most important among all the 19th century ideology because, it stemmed from the Enlightenment idea that man possessed a certain set of basic rights and liberties which were conferred to each individual upon their birth and could not be infringe and it includes, various rights and freedoms, including the right to free speech and the right to private property.