B&O Unlocked: B&O No. 3684 Diesel Locomotive

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!

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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:

Visit on Wednesday, June 18 for a special $10 Admission Day!

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

More about the B&O Unlocked Series

America 250: B&O Unlocked

Celebrate America’s Story—One Railcar at a Time

The B&O Railroad Museum’s annual Unlocked series returns—this year with a special tribute to America’s 250th anniversary. Each month, step inside a different piece of rail history and experience the stories that helped build a nation. In honor of this milestone, American Freedom Train No. 1 will be opened twice in 2026—January and July—offering a rare chance to celebrate the spirit of freedom and innovation that defines America’s rail legacy.

You’ll also have the opportunity to step inside the newly restored B&O No. 3316 “Washington” Observation Tavern Car.

Become a B&O Member and 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.

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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.

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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.

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B&O No. X-4055 Camp Car

April 16, 19 & 20

The B&O No. X-4055, also known as the B&O No. 4723 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.

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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.

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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.

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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.

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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.

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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.

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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.

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