Chart coverage by US river

A river is charted differently from a coast, and it is run differently. The water is a managed pool rather than a tide, the traffic is commercial tows that need the whole channel, and the thing that stops you is usually over your head rather than under your keel. Helm builds a separate pack for each river so you carry the waterway you actually run.

Across the 15 rivers below that comes to 3,209 charted bridges, 1,308 overhead cables, 8,077 charted lights and 514 charted lock features. Pick your river to see what its own pack carries.

River	Bridges	Overhead cables	Lights	Lock features
Ohio River	734	186	1,793	134
Upper Mississippi River	501	114	1,527	126
Tennessee River	397	357	879	41
Illinois River	307	136	948	24
Missouri River	241	46	420	0
Kanawha River	215	65	282	24
Monongahela River	207	87	484	39
Arkansas River	168	67	555	52
Allegheny River	118	41	209	21
Black Warrior-Tombigbee	88	65	100	11
Lower Mississippi River	69	21	447	6
Red River	51	24	80	15
Ouachita River	50	42	171	12
Green River	33	30	107	9
Atchafalaya River	30	27	75	0

Counted layer by layer from the chart packs themselves. Lock features are counted as the chart draws them, with chambers, gates and dams as separate objects, so the figure is not a count of lock and dam sites.

Coastal water and the Great Lakes

The rivers above are the inland commercial waterways. Salt water, the intracoastal and the Great Lakes are packed separately and counted on the regions page. Inland lakes are built from state elevation surveys rather than from charts, and are counted state by state on the lake charts by state page.

Common questions

Which US rivers does Helm chart?

Helm builds a separate inland pack for 15 commercial rivers, listed on this page, and they carry 3,209 charted bridges and 1,308 overhead cables between them. Lakes and the intracoastal are covered separately.

Does Helm show overhead clearance on rivers?

The packs carry the charted bridges and overhead cables as the inland charts draw them, 3,209 bridges and 1,308 cables across the 15 rivers. On a river the height over your head decides more passages than the depth under you, which is why the counts are published here per waterway.

Where do the numbers on these pages come from?

Every count is taken from the chart pack itself, layer by layer, out of the official inland electronic navigational charts the pack is built from. Nothing on these pages is an estimate.