The correct answer is The Department of the Interior. It was formed in 1849, a year after the Mexican war. The Department of state was formed in the 1700s, while the Bureau of Indian Affairs was formed in 1824, which was 25 years before the Department of the Interior and before the Mexican War.
In August 1805 Lewis and Clark were looking for the Shoshone Indians. The Corps (Lewis and Clark's expedition party) needed horses to cross the Rockies and the Shoshone had them. Sacagawea, a member of the Corps, was Shoshone, but she had been kidnapped by another tribe many years before.
The Corps were still recovering from their portage around the Great Falls of Missouri. Morale was low. Lewis and three men were scouting ahead when they finally met a band of Shoshone. They were the first white men the Shoshone had ever seen.
hope this helps in anyway! :)