Adams, 63, has published seven books, including "Roadside Markers in West Virginia" in 1995.
He is retired from a job as an editor at a Long Island weekly newspaper. Before doing that, he was a school principal.
He and his wife of 43 years, Mary Kate Adams, moved to Shepherdstown about five years ago. She currently works with the Berkeley County Senior Services.
Adams said he's long had an interest in history, particularly the Civil War. After moving here, he wrote a book about the Civil War in Washington County.
He frequently rides his bike in Antietam National Battlefield, where numerous roadside markers are placed.
The idea for a Maryland book came to him during one of his bike rides, he said.
The state has more than 700 markers and records of them has been kept over the years, shuffled from one state agency to another, he said.
He found the listing of markers in Crownsville, Md., chaotically kept in notebook binders, folders and scattered about a storage room.
Adams said his book is not the definitive listing of all roadside markers in the state, but he hopes to improve on the listing in future editions.
One of the most "chillingly interesting" he found was a roadside marker in Prince George's County marking the site of an infamous dueling ground during the early 1800s.
Gentlemen fought and killed each other at the site to settle disputes of honor, he said.
Some of the markers blaze a trail, such as those following the path taken by Booth after he assassinated President Lincoln, Adams said.
His favorite is the marker outside the Kennedy farm, where the abolitionist Brown and his supporters gathered in preparation for their raid on Harpers Ferry, W.Va.
"It shows you how divided the nation was during that time, to have those two extremes in the state," Adams said.
Other roadside markers record forgotten people and events, he said.
People drive by the sites now where history occurred without realizing the connection to the past, he said.
"Originally when cars were slower and it was mainly back roads . . . people would pull over and picnic next to the sites," Adams said.
The self-published book is available at some local bookstores or by sending a check for $16 to Adams at 201 Ryan Court, Shepherdstown, W.Va., 25443.