A brief visual history of MARC cataloging at the Library of Congress.

The Library of Congress has released MARC records that I'll be doing more with over the next several months to understand the books and their classifications. As a first stab, though, I wanted to simply look at the history of how the Library digitized card catalogs to begin with.

A couple notes for the technically inclined:
1. the years are pulled from field 260c (or if that doesn't exist or is unparseable, from field 008). Years in non-western calendars are often not converted correctly.
2. There are obviously books from before 1770, but they aren't included.
3. By "books", I mean items in the LC's recently-released retrospective (to 2014) "Books all" MARC files. http://www.loc.gov/cds/products/product.php?productID=5. Not the serial, map, etc. files: the total number is just over 10 million items.

See after the break for the R code to create the chart and the initial version Jacob is talking about in the comments.