From 1814, Christiania became the capital of Norway, which had regained partial independence from Denmark and entered a union with Sweden. Industrialization started in 1840, initially along the Aker River. The population grew rapidly, and new infrastructure was built. Commercial activities increased, and in 1854 the railway station was opened, connecting Christiania to Lake Mjøsa via the Hoved Line. In 1835, the population was 18,000; by 1890, it had reached 151,000. From 1878, the Oslofjord was kept permanently open with icebreakers. By 1900, Kristiania was the leading shipping city in the nation, and among the most important in the world.