Although more like 20 pages than 1800 pages, my family recently use FOIA to obtain my grandfather's FBI file. It was apparently opened after someone at a party he attended overheard him speaking about the Rosenbergs and reported to the FBI that he "sounded like a communist". It turned out to be pretty interesting.

If you have any family members that were involved with the anti-war movement or with the labor movement, you may want to file your own FOIA request. They were surprisingly responsive. Not within the statutory limits mind you, but less than a year.