We saw several national landmarks on our summer vacation: Mount Rushmore, the Washington Monument, and the Grand Canyon.
A colon should be used before listed items when the sentence can actually stop at the colon. This sentence is a complete sentence before the list of landmarks. The colon allows the landmarks to be listed after, but still connect them to the sentence. Option 1 should have a colon after battles and Option 3 should have a colon after college for these same reasons.
