Tracing The ICW

By Bill Parlatore
Published: October/November 2013

It's the yellow brick road for thousands of boaters along the Intracoastal Waterway, but the ICW's magenta line is sorely in need of an update.

Origins Of The ICW And The Magenta Line

With the help of BoatUS, I contacted the NOAA Office of Coast Survey (OCS), our nation's chief charting agency, and began a conversation with Communications Specialist Dawn Forsythe, who worked my questions through the staff of OCS cartographers. She confirmed that all U.S. nautical charts are the responsibility of the Office of Coast Survey, which maintains source data for all forms of paper and electronic charts. All charts found in chart kits, guidebooks, and electronic chartplotters originate from this agency.

The Atlantic and Gulf Coast Intracoastal Waterways were assembled piecemeal beginning before the turn of the last century but were not fully constituted with those names until 1939 in the case of the Atlantic, and 1949 for the Gulf. One of the larger milestones along that journey occurred with the passage of the River and Harbor Acts of 1902 and 1903 that authorized studies to join various sections of open water with privately constructed canals, and locally dredged channels supported by tolls, and publicly funded land cuts. At the time it was imperative to find continuous water routes for defense and commercial needs, as shipping along treacherous coastlines had serious risks.

The U.S. Coast and Geodetic Survey (USC&GS), a predecessor of NOAA, published its first edition of the Inside Route Pilot in 1912. Included were charts that showed protected routes inside the coasts from New York to Key West and from Key West to Texas. This publication met the needs of the motor-powered vessels that took advantage of increasingly modern navigation for commercial travel. The Inside Route Pilot included hand-drawn red lines highlighting routes on the charts. It was the precursor of what we now know as the magenta line. Interestingly, a controlling depth of just three feet was sufficient for the time. Six editions of the Inside Route Pilot were published between 1912 and 1935. The updates highlighted changes in lights and buoys, variations in typography, and new hazards to navigation. The red-line markings remained much the same over these 23 years.

Now, let's move forward to 1935, and America's struggle to get out of the Great Depression. Among the many government programs to stimulate the economy and get people working, the Public Works Administration more than tripled the USC&GS budget. These additional funds greatly increased the agency's ability to do its job, and one project it undertook was to modernize nautical charts. The agency doubled the number of workers available to conduct field surveys of the waterways. Noting the increasing demands of commercial traffic, they also changed the controlling depths to fit the draft requirements of this traffic. The surveys specified depths of no less than seven feet on the Atlantic waterway and no less than six feet out to Corpus Christi. The substantial investment in this project greatly improved the charts and the entire waterway system, which now stretched from New York to Texas. The new charts included updated magenta-line detail. In the years since, authorized depths have been modified and additional surveys have been conducted, but for the most part, the magenta line has not changed since 1936.

Where Does That Leave Us?

Surprisingly, the magenta line has not been "owned" by any federal agency for quite some time. It seems to have gotten lost among the other realities that define the national maritime landscape. Today the Atlantic and Gulf ICW systems are managed by the U.S. Army Corps of Engineers. NOAA Office of Coast Survey doesn't even survey the ICW, except when requested by the Corps of Engineers in special interagency instances, as in the case of post-Sandy storm damage assessment.

But that isn't to say the magenta line has been untouched. For some period of time, inaccurate portions of the magenta line were simply deleted. It was felt that nothing was worse than providing incorrect information, so it was better to remove these areas rather than keep them on a chart to mislead mariners. One might argue this made sense, but it was a short-term fix that ignored the grander vision of improving the overall system. In March, Commander Shepard Smith became the new chief of Coast Survey's Marine Chart Division. With his appointment comes opportunity. CDR Smith's office wants to review the current state of the magenta line, assign responsibility for it, and develop a plan to make it an accurate and safe navigation tool for all mariners. These efforts will likely involve the U.S. Power Squadrons, U.S. Coast Guard Auxiliary, perhaps even BoatUS His office expects to invite the boating community to participate.

The concept of a protected inland waterway along our coast is as valid today as it was a century ago. A national treasure, wondrously rich in history and natural beauty, the ICW still offers outstanding utility for commercial and recreational use, and is a lasting tribute to our nation's maritime heritage. As for the magenta line, good things are on the horizon for a navigation tool that hasn't had much attention in almost 80 years. Stay tuned.End of story marker

Bill and Laurene Parlatore founded PassageMaker magazine, and enjoy boating in many forms, including recent adventures on the French canals.

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Planning To Travel The ICW?

1. The magenta line should be treated as a general guideline only. It shows a boat operator where the next leg of the waterway is, especially helpful when transiting from one body of water to another.

2. Whenever the magenta line conflicts with the surrounding landscape, navigation aids, or your sixth sense, always stick to the navigation aids and information you can see in front of you. Never choose the magenta line over buoys marking the safe route around or through a hazard or obstruction.

3. All available charting comes from the source data owned and managed by the NOAA Office of Coast Survey, so any inaccuracies that exist will be the same on any charts you purchase whether they're paper or electronic, until source data is changed by NOAA OCS.

4. If you find an error with the magenta line on your chart, report it to the Office of Coast Survey at

5. Wondering if your electronic charts are up to date? On a chartplotter, pull the chart chip and check the date or go to the main screen and look for "info" or "about." On mobile devices, click the little "i" symbol somewhere on the chart, usually the lower right-hand corner.

Online Extra! icon Online Extras!

Curious where the NOAA ships are currently surveying? Download survey priorities here. Or what it's like to be an NOAA hydrographic officer? See William Winner's full interview and info on what NOAA's hydrographic ships do.


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