James Fanelli:

For the first time in nearly four score and seven months, Gettysburg National Military Park needs guides, so the National Park Service will administer an exam this month. The test, last given in 2017, has gained mythic status among Civil War buffs for its degree of difficulty and slim passing rate. It requires an encyclopedic knowledge of the 1863 battle, as well as a firm grasp of the lead-up to the war and its aftermath.

The competition is so tough—and a spot as a guide is so coveted—that some test takers spend years studying for it and even upend their lives to be closer to the historic battlefield.