Final answer:
Bolivia is the country that had access to an ocean in 1830 but became landlocked after losing the War of the Pacific to Chile.
Step-by-step explanation:
The country that had access to an ocean in 1830 but is now landlocked is Bolivia. This happened as a result of the War of the Pacific (1879-1883), in which Bolivia and its ally Peru went to war with Chile over a mineral-rich coastal area. After losing the war, Bolivia ceded its coast to Chile and has been landlocked ever since. Although Bolivia attempted to regain access to the Pacific Ocean, these efforts have been unsuccessful, and the country remains without direct access to an ocean.