“I hope this new collection will help open people’s eyes to what is in the holdings of our national library,” Ms. Potter said. “I’m glad these books exist and have been well taken care of.” And they can take children — and their parents and teachers — into a wide variety of stories and conversations and histories.

The first public reading of the Declaration of Independence in Massachusetts was performed by Isaiah Thomas, who had been apprenticed at the age of 6 to a printer, and had learned to read, so the story goes, from the blocks as he set type, copying documents before he actually knew the letters. “He was just learning the shape of the letters and copying what was on the sheet, they even had to build him this little bench to walk back and forth on,” said Jacqueline Coleburn, the rare book cataloger at the Library of Congress.

Thomas, who grew up to be a printer himself, was publishing a patriotic newspaper as the American Revolution approached, and his name was on a British list of those to be executed. And in July 1776, on the way from Philadelphia to Boston, he stood on the steps of the South Church in Worcester, and read the new Declaration aloud to the approving crowds.

In the newly independent United States of America, Isaiah Thomas continued in the book trade, and he printed the oldest book in the Library of Congress’s new online collection, “A Little Pretty Pocket Book,” printed in 1787. The book had initially been co-authored and published in England in 1744 by John Newbery, often described as the founding father of modern children’s literature, whose name is enduringly famous because of the Newbery Medal given every year; Thomas initially imported the book, and then began printing it himself, becoming the first American printer to publish specifically for children. Although it came from England, the book is also famous because among its rhyming descriptions of various games, it contains the first mention of one called “base-ball.”