“Incunabula” is a Latin term meaning “swaddling clothes,” and generally applied to the origins of anything. But in English it has one meaning: the books from the earliest age of European printing, up to the completely arbitrary year of 1500. These fifteenth-century editions are rare and extremely valuable, and every book collector covets them.
Early American imprints—that is, printed books and materials from the English colonies in North America and from the first years of the United States—are also rare and valuable. In fact, the most valuable printed book in the world is not an incunable but the Bay Psalm Book, printed in Cambridge (Massachusetts) in 1640. Dr. Boli proposes a new term for these early American imprints: American incunabula, a term that no one else seems to have come up with. And just as the cutoff for incunabula has for centuries been set at the completely arbitrary date of 1500, so we shall set the last date for American incunabula at 1800.
Why 1800? It is not a completely arbitrary date. The printing business evolved gradually in America, but the year 1800 is in the middle of several large changes. First of all, 1800 was about the time printers abandoned the long S—an abandonment that, by historical standards, was very sudden, so it makes a very easy visual distinction to look for. Second, Americans were beginning to cast their own type, which previously had to be imported from England. Third, the recent independence of the United States was encouraging native publishing. Today, if one finds a book in the United States that was printed in the 1600s or 1700s, it is much more likely that it was printed in England or France than in North America. At some point around 1800, that ceases to be true, and American books predominate.
In short, the period up to 1800 is a period when American books are scarce and at least moderately valuable; after that they become common and cheap. If you have a book printed in the English colonies or the first quarter-century of the United States, it is probably worth some money.
The good news, though, is that anyone can build a digital collection of such books, and Dr. Boli has done just that in his new page of American Incunabula. We begin, of course, with the Bay Psalm Book, and continue all the way to the first books printed west of the Alleghenies, namely in Pittsburgh, where John Scull (with encouragement from Hugh Henry Brackenridge) set up a press in the 1780s. The books are arranged chronologically, and chosen according to the usual standards of the Eclectic Library; which is to say that the collection includes whatever interested Dr. Boli for his own whimsical reasons.