No state touches more of the Mississippi system than Kentucky: the Ohio runs its entire northern border, the Mississippi its western tip, and the Tennessee and Cumberland cross the west of the state, all four inside the 33 CFR 83.03(n) definition. That makes the river provisions the ordinary case here rather than the exception, and worth knowing by number for a closed-book module — a downbound vessel with a following current holds the right of way and proposes the passage under 83.09(a)(ii) and 83.14(d), and a vessel crossing the river gives way to one running up or down it under 83.15(b). Kentucky Lake and Lake Cumberland are impoundments of the Tennessee and the Cumberland, and an impoundment is precisely where the classification should be confirmed with the OCMI rather than carried over from the river that fills it. REC Memphis takes Kentucky files.
33 CFR Part 80 draws no demarcation line in Kentucky. Its 106 sections cover the Atlantic, Gulf and Pacific coasts, Puerto Rico and the Virgin Islands, the Pacific islands and Alaska; a state with no coast has no section, which is itself the answer.
Western Rivers (the Ohio, Mississippi, Tennessee and Cumberland Rivers) are defined at 33 CFR 83.03(n) and carry Inland Rules provisions the rest of inland water does not: 83.09(a)(ii), 83.14(d), 83.15(b) and the towing-light exception at 83.24(j).
This decides which rulebook you steer by, not where your credential may operate: the route limit is the 46 CFR Part 7 Boundary Line, and the two lines are not drawn in the same place. How the two lines differ · International Rules · Inland Rules
33 CFR Part 80 and the Part 83 definitions above read from eCFR on 12 Aug 2026. Any specific water is a determination for the cognizant Coast Guard Officer in Charge, Marine Inspection.