Lines of Equal Magnetic Declination on the coast of the United States for the year 1850

A simple map of the entire United States showing the lines of equal magnetic declination along all coasts. IMPORTANT NOTE: All of our United States Coast Survey (USCS), United States Coast & Geodetic Survey (USC&GS), and similar maps and charts have been professionally unfolded and flattened using humidity baths, semi-permeable membrane, and drying blotter techniques. Most others you typically see on eBay have not been, and worse, are quickly and crudely unfolded for the low-quality photos you see. Unfolding these maps in that way is damaging and weakens them. Please be aware.