I got this idea from a Charles Bukowski website where his FBI files are posted. I wondered if Jack Kerouac has an FBI file, and some Googling didn't get me anywhere. Crystal turned me on to this website - Get Grandpa's FBI Files - where you can generate letters to the FBI under the Freedom of Information Act to get copies of any dead person's FBI file.
I sent requests for Jack Kerouac's FBI files to the FBI offices in San Francisco, Boston, New York, and Winchester, VA (the main records office). Today I received the acknowledgement letter below.