This is free at the NOAA web site:
https://nauticalcharts.noaa.gov. Do not get in a rush and click on the "ENC Viewer" to start; it will not
work to download anything useful. Instead, on the main page, click on the CHART LOCATOR which is quite prominent. With it the
ENC (Electronic Nautical Chart) locator window will open. Yes, it does look like the above mentioned
ENC Viewer, but works seamlessly for a
government bureaucacy generated application. Zoom in and select the chart you want that has a red box around it, unless it is a smaller chart in a higher resolution (or larger scale) within it which will have a yellow border if it was selected. A window will apear to the right. There may be other related
charts suffested. In it the chart desired can be ascertained. After making sure, just click on the "ENC" in the white section and an User Agreement will appear, and will do so for every chart you select, so after the Blue typeface,"OK" COLOR="blue"]OK[/COLOR] is selected the chart will download in a compressed (.zip) format. (The User Agreement will not go away. If you do not delete the page(s), they will build up in the browser window.) The compressed files that are downloaded will need to be opened and the contents placed in a folder for the relevant files, not in
OpenCPN, but in a folder that the "Chart" button in
OpenCPN can access outside of its own folder. To save some frustration and memory in your computer, use one folder with sub-folders, as suggested in the OpenCPN Manual for CM93, ENC, and RNC
charts, and sub-folders if you wish, for particular areas within them. Do not copy and paste the particular map ENC_ROOT folder, rather open it and copy and paste just the file folder, e.g. "US3GC06M" from within the root folder. This will be installed by OpenCPN when selected after selecting the Chart symbol in OCPN. My apologies for being pedantic to those who are sophisticated in OCPN, but the manual is not written for those of us who could have saved alot of time had it been given more attention to detail. My MOS was map draftsman >50 years ago.