John David Hiteshew Sr. and John David Hiteshew Jr. — both known as David — spent four years walking and exploring hundreds of miles of Maryland railroad trackage to document the industrial infrastructure and physical characteristics of the Baltimore & Ohio Railroad, the nation's first common-carrier railroad, which began building westward from Baltimore in 1827.

They were armed with walking shoes, notepads and a digital camera used to photograph trackage, alignments, curves, grades, tunnels, culverts, bridges — both stone and steel — yards, signals and wayside structures affiliated with the railroad.

They also recorded stations, towers, shop buildings, and the remains or foundations where structures had once stood. No detail, however mundane or pedestrian, escaped their attention.

And in the process, father and son, both Catonsville residents, managed to rack up an impressively detailed archive of more than 50,000 images.

After documenting the B&O lines as far west as Harpers Ferry, W.Va., they turned their attention to the former Pennsylvania Railroad mainline, now part of Amtrak's Northeast Corridor, between Baltimore and Havre de Grace.

"We had just started on the Pennsylvania when dad got sick with cancer," David Hiteshew Jr., a fuel truck driver, said in an interview the other day. "We found some old mileposts that were far away from the original alignment and several old stone culverts from the line's original route."

The elder Hiteshew, 71, who was a retired National Cash Register technical service engineer, died late last month. Born in Baltimore and raised in Edmondson Village, he had two lifelong hobbies: railroading and photography.

"When we were boys, Dad bought us Lionel trains and we built layouts, but David always liked real trains," said a brother, Richard A. Hiteshew, also a Catonsville resident.

After undergoing back surgery several years ago, the elder Hiteshew's physician suggested he start walking to help in his recovery.

Because the B&O's Old Main Line coursed through Patapsco Valley State Park near his home, he went trackside to walk and photograph what he found along the right of way.

He was soon joined by his son.

"We started in 2007," David Jr. said.

They walked, studied and photographed virtually all of the B&O's trackage in Maryland.

They explored from Mount Clare to Harpers Ferry, the Old Main Line from Relay to Point of Rocks, the Capital Subdivision from Baltimore to Washington, the Metropolitan Subdivision from Washington to Point of Rocks, and the abandoned Georgetown Branch that ran from Georgetown to Silver Spring.

"We'd park the car and walk about three miles. And remember: We had to walk the three miles back," the son said. "And for safety reasons, we never walked on the track but alongside it. We were very careful."

To their delight, they discovered long-forgotten weed-choked gradings, former alignments and original granite track stringers that dated to the 1820s and were used before wooden and today's concrete cross ties came into use.

Horses that pulled the cars in those days walked in the middle of the parallel stones on which the iron strap rails rested and flanged wheels rolled.

The pair documented the sites they were photographing with elaborate notes and, once home, downloaded the photos they had taken.

Their consistent and orderly perambulations would begin where they had previously left off, and took place only during warm months.

Along the way, they discovered forgotten infrastructure that reached back to the B&O's earliest days.