Final answer:
Belgium gained independence from the Netherlands in 1839.
Step-by-step explanation:
The country that gained independence in 1839 from the Netherlands is Belgium. During the Napoleonic period, Belgium was controlled by the Dutch. However, in 1830, a revolution broke out in Belgium against Dutch rule, leading to its independence in 1839. Belgium became a rapidly industrializing nation in the 1830s, with usable waterways, coal deposits, and a skilled workforce.