The Library of Congress provides CIP data blocks only to publishers who fulfill certain requirements. Most indies won’t meet those requirements.
However, anyone in the U.S. can obtain a PCN for their book. A PCN is a preassigned control number. It is equivalent to the LCCN, the Library of Congress catalog number. If the LOC later decides your book is important enough, they’ll use that number for their record.
You can include the number on your book’s copyright page:
If you have a PCN, you can obtain a PCIP (Publisher’s Cataloging-in-Publication) data block. There are several companies that will provide them.
I’ve obtained reasonably priced data blocks from Adrienne Bashista:
Apply for the Library of Congress PCN program here: