B&O Unlocked: B&O No. 3684 | B&O Railroad Museum

The B&O Railroad and General Motors helped pioneer diesel-electric technology in the early 20^th century. In the years preceding the second world war, the demand for these new diesel engines steeply rose.

The B&O No. 3684 was the first locomotive to arrive from a purchase of 16 GP-40 diesel-electric engines from the General Motors Electro-Motive Division and the first B&O locomotive equipped with an AC alternator.

Today, the No. 3684 remains operational and this month, you’ll be able to step inside!

Learn More about this Collection item

Tours:

Tours will be available between 10 AM – 4 PM.

Please note: This tour requires participants to climb stairs and walk on uneven pathways. A virtual tour will be available on-site via QR code. Docent Tour Guides stationed near the locomotive can answer any additional questions about the history and physical description of the locomotive. Small children must be accompanied by an adult guardian at all times.

Admission:

Included with Museum Admission. FREE for B&O Members.

More about the B&O Unlocked Series

B&O Unlocked returns in 2025!

Step into a variety of our historical marvels as their doors open for a limited time! Each month, you will have the chance to explore the interiors of a new museum collection piece and hear about their amazing histories.

This year, you can expect a chance to step inside nine new pieces and two fan-favorites!

To join us on this journey through history and save, purchase a B&O Membership receive free admission for each collection piece. Don’t miss this opportunity to unlock the doors on these historic pieces!

Step inside the complete 2025 series!

B&O No. CE-15 Tunnel Clearance Car

January 15, 18 & 19

The CE-15 is believed to be the world’s only surviving tunnel clearance car and serves as a testament to a pivotal moment in locomotive design.

Learn More

B&O No. CE-10 Electric Switcher

February 19, 22 & 23

The B&O No. CE-10 worked on the small rail network of Fells Point to keep Baltimore industry moving.

Learn More

GC&E No. 1 “Shay”

March 19, 22 & 23

The GC&E No. 1 “Shay” is an asymmetrical engine designed to navigate the uneven tracks and sharp curves of logging country.

Learn More

B&O No. 4723 Camp Car

April 16, 19 & 20

The B&O No. 4723, also known as the B&O No. X 4055 and nicknamed “Thendara” was originally constructed as a sleeper car and later refashioned to serve as a Maintenance-of-Way (MOW) camp car in the 1960s.

Learn More

B&O No. C-2943 Caboose

May 21, 24 & 25

The B&O No. C-2943 is an example of an I-7A caboose, which is known for its steel body and protruding bay windows.

Learn More

B&O No. 3684

June 18, 21 & 22

The B&O No. 3684 was the first locomotive to arrive to the B&O Railroad from a purchase of 16 GP-40 diesel-electric engines.

Learn More

WM 195 Switcher

July 16, 19 & 20

The WM No. 195 is a multi-purpose engine made to travel as fast as a mainline locomotive and was used for over two decades to pull heavy coal trains.

Learn More

B&O No. B-29 Jordan Spreader

August 20, 23 & 24

The B&O No. B-29 is a “Jordan Spreader,” a type of maintenance car that is considered by some to be the earliest type of railroad maintenance equipment.

Learn More

B&O No. 633 Switcher

September 17, 20 & 21

The B&O No. 633 is a diesel switcher of the SW-900 model that still occasionally operates at the museum.

Learn More

B&O No. 3302 “Edward G. Hooper” Observation Lounge

October 15, 18 & 19

The B&O No. 3302 “Edward G. Hooper” Observation Lounge, serves as a reminder of luxury passenger service and traveled with the Royal Blue and the Ambassador.

Learn More