Counting records at Mary Ferrell

[First posted on March 10, 2018, at]

I’ve been doing some record counting at the Mary Ferrell website (MF). This is possible through a tool added to MF in 2016, called the JFK Database Explorer. According to the FAQ for the Explorer, it is based on a copy of NARA’s on-line finding-aid database for the JFK Assassination Record Collection.

The copy was made by Ramon Herrera in the summer of 2015 and has 319,106 records.1JFK Database Explorer FAQ: Is the Database Complete and Up-to-Date? Surprisingly, MF quotes NARA’s Martha Murphy, as saying that NARA’s finding aid database has only 318,866 records, 240 fewer than Herrera’s copy. MF then observes that ‘the reason for this discrepancy is as yet unknown.’

Total collection size is of course a very useful thing to know, and on this page of the Explorer, MF gives a helpful break-down of total records counts in the Explorer by prefix. NARA assigned numbers to each agency providing records to the Collection, and it uses these as prefixes to the record numbers for each item in the collection. There are 37 prefixes, from 104 (CIA) to 208 (Senate Permanent Subcommittee on Investigations).

Adding up the number of records MF gives for each of these prefixes, however, the total is 318,733, which matches neither the Explorer total given by the FAQ, nor the NARA total given by Murphy.

I would be curious to know the story on this. I went through the sub-pages for each prefix on MF; these provide a further break-down ‘disk-by-disk’, using record counts on each floppy disk that NARA used to get record information from each agency. This gave me the same figure: 318,733. (I’d rather not count the individual records one by one.) Perhaps I should write to Mary Ferrell as well as NARA.


Regarding the alleged discrepancy between the number of records that Herrera scraped and Murphy’s estimate quoted by MF, NARA now states that there are 319,106 records in its on-line finding-aids database.2 This number matches the count MF gives for Herrera’s copy. I checked the Wayback machine, and NARA’s new estimate was apparently added at the end of October 2017.3 The NARA page also now says that the finding-aid database was last updated May 12, 2008. This is puzzling, and I will comment on it in the not too distant future.