We sing "God Bless America" instead of "God Bless Columbia" because Amerigo Vespucci got a better press than Christopher Columbus, according to a new exhibit at the National Museum of American History.

Vespucci came to these shores seven years behind Columbus, but he was a quicker study and a better promoter. He realized, as Columbus never did, that a "new world" had been found; and his accounts of his voyages sizzled with descriptions of wild sex and cannibalism among the natives.

Vespucci's travel letters reached Saint- Di,e, in Alsace-Lorraine, where a new edition of Ptolemy's atlas of the world was being prepared by the "Vosges School" press in 1507. New wood plates were cut, and when the thing was run off, the Mundus Novus mainland bore the name "America." It sold like hotcakes, and other mapmakers picked up the name, so that by the time the primacy of Columbus was recognized, the usage was firmly established. Which is why the District of America is not the capital of the United States of Columbia.

Although a thousand copies of the 1507 map were said to have been printed, none is known to have survived. A few years later there was another press run, using the same plates. The single known copy of this edition turned up in 1901 in Wolfegg Castle in southern Germany, bound in board covers along with the only known copy of the 1516 Carta Marina, a sea chart published by the same group of scholars. They were already having second thoughts and left "America" off the chart, but it was too late. And anyway, the Indians discovered America, so what the hell. The reason we're bringing all this up now is that the book containing the "American" map has just gone on public view for the first time ever, courtesy of Max Willibald, Erbgraf zu Waldburg-Wolfegg. Castle and book have been in the count's family since the 16th century, and the only other time they've let the thing out of the house was in 1903, to be copied. Because the volume has been declared a German national treasure, the two-year loan had to be approved by the government. Although its existence has been known for 80 years, little scholarly detective work had been done on the map before it arrived at the Smithsonian last summer. Curators Silvio Bedini, Helena Wright and Elizabeth Harris have been all over it like white on rice ever since; their preliminary findings make fascinating reading, and lots of it, around the walls of the exhibit. Many questions remain about the map, as the scholars frankly point out.

It's a splendid gallery, although the lighting of some of the showcases and particularly of the centerpiece volume is necessarily murky, because even moderate illumination degrades such materials.

But the visitor will come away wanting to know more about Max Willibald and family. Imagine having something like this lying around your place for over 400 years. THE NAMING OF AMERICA -- At the National Museum of American History, 14th and Constitution NW.