www.loc.gov/acq/

The Library of Congress acquires materials in all formats–books, periodicals, maps, music, prints, photographs, recorded sound, videos, electronic, etc.–and in all subjects, except technical agriculture and clinical medicine, from all over the world. We use six methods to acquire materials–Cataloging in Publication, Copyright, Exchange, Gift, Federal Transfer, and Purchase. The collection is shaped by the Library's Collection Policy Statements and totals over 138,000,000 items.

>all subjects, except technical agriculture and clinical medicine

a couple interesting exceptions there