The Gilbert Journals were written by Johnathan Gilbert back when he was alive in the 18th century. They contain information about his life story and the existence of vampires. Elena, Jeremy, Anna, and Alaric have read the journals. There is also a separate set of journals written by Johnathan Gilbert that were read by John Gilbert, but these aren't seen.
The journals were first mentioned to Jeremy by Jenna when he said that he had to do a history report. They were in a closet in his parent's old room. Jeremy later writes a extra credit history report on vampires, with the nudging of Anna.
Alaric asks to borrow the journals wanting to find out more information on the vampires. Later on Anna wants to barrow it to try to find out how to unlock the vampire tomb and asked Jeremy at the 50's dance. When Noah threatens to kill Jeremy and messes around with Elena, Stefan and Damon ask him information about opening the tomb. He reveals that the journal has information on where Emily's Grimoire is located and afterwards they kill him. They start looking for it, but Alaric still has it. Alaric photocopies the book in the high school and afterwards Anna takes it. Stefan later steals the photocopy Alaric made.