The National Archives Catalog is our online portal to the records held at the National Archives and
information about those records. It's our main way of describing our holdings so that you can
learn about what we have. The Catalog is also how we provide access to electronic records and
digitized versions of our holdings. So it's a great resource even if you're unable to visit
a facility in person. An important thing to understand is that only a small percentage
of our holdings are available online. Not every page of records we have at the National Archives
is in our Catalog. Our Catalog also searches across multiple National Archives resources at
once. So performing a search will often retrieve digital files of records, record descriptions,
but also web pages, blog posts, and Presidential Library websites. The other exciting feature of
our Catalog is that it allows you to participate in enhancing historical records through tagging,
transcription, and commenting. I first want to explain how records are organized or arranged
at the National Archives. We call this record hierarchy. Understanding the hierarchy of the
types of descriptions you see in the Catalog will help you get a feel for how records are organized
and will also help you search for and identify them when you see them in the Catalog. And when
you find a document of interest it can help you find more like it. I like to think of the National
Archives as the nation's filing cabinet, which can be a helpful way to visualize how we organize
records. At the very top of the hierarchy, we have Record Groups. Each Record Group comprises
the records of a major government entity: usually a bureau or an independent agency that created
or maintained these records. For example, Record Group 255 is records of the National Aeronautics
and Space Administration. It might be helpful to think of a Record Group as an entire file cabinet.
It has many different drawers and folders and items within those drawers, but the records are
united by the Federal agency that created or maintained those records. This is the largest
bucket and a very high level grouping of records. Another thing to note is that records within one
record group are not always found in the same location. The National Archives is not just in
Washington DC. We have various regional archives and Presidential Libraries across the country,
and records within a Record Group may be held at one or more of those locations. The next level in
our hierarchy is Series, which further organizes records of a government agency. You can think of a
series as a drawer within a file cabinet. Records that have the same function or were created by the
same activity are in a Series together. An example of a Series is "Mission Photographs Taken During
the Space Shuttle Program, 1981 to 2011," which is part of Record Group 255: Records of NASA. A
Series can be one box, or it could be thousands of boxes. You can find the extent of a series
by looking at its Catalog description. 95% of our records are described at the series level.
This means you can find out basic information about the records including how big it is: from
a few linear inches, to thousands of linear feet, from its description in the Catalog. You can also
find out where the records are located. A File Unit is the next smaller level in our hierarchy.
You can think of file units as folders within a drawer. They're not always just one folder;
sometimes the records may need to be housed in multiple folders. A file unit could even
be a bound volume. An example of file unit is "STS 47" which was the 50th space shuttle
mission of the program. An item is the lowest level of description we have. It represents an
individual archival record and all the pages that make it up. Items can be letters, memos,
reports, or photographs and they could also be sound recordings or films. For example,
this photograph in our Catalog of astronaut Mae Jemison is one item within the file unit "STS 47"
from the series "Mission Photographs Taken During the Space Shuttle Program" which is part of Record
Group 255: Records of NASA. You can always see this record hierarchy here in our Catalog. When
you're looking at a description, you'll notice the hierarchy in the upper left hand corner.
This shows you where the item lives within the hierarchy I just discussed. Each level is a link,
so clicking on each of these links will allow you to back up to the record group, or series,
or file unit where you can find more information. For instance, if you want to find more records
like that when you're looking at, backup to the file unit or series where you can find similar
records. The holdings of the National Archives are growing all the time and we're adding more digital
objects to our Catalog each week so you're likely to find something new every time you search.