Conversation so far:
What was the Third Expedition for Kit Carson?
In 1845, Carson guided Frémont on their third and last expedition.
What did Kit Carson and John Charles Frémont do on their third expedition?
They went to California and Oregon. Frémont made scientific plans, but the expedition appeared to be political in nature.

Question: What did they do in California and Oregon?
Self-contained rewrite: What did Kit Carson and John Charles Frémont do in California and Oregon?