The Coast Guard is part of the Department of Homeland Security. Before that it was part of the Department of Transportation and before that, the Commerce Depart

The Coast Guard is part of the Department of Homeland Security. Before that it was part of the Department of Transportation and before that, the Commerce Department. (It was originally established to collect custom duties.) It's only part of the "military hierarchy" in times of war, such as World War I and World Way II, when it falls under the Navy.