Monocacy (/məˈnɒkəsi/) is a passenger rail station on the MARC Brunswick Line between Washington, D.C. and Frederick, Maryland.

[citation needed] Monocacy station is located at 7800 Genstar Drive, a cul-de-sac with a large parking lot off the east side of Maryland Route 355 in Frederick.

[citation needed] MTA Maryland Commuter Bus TransIT Services of Frederick Monocacy Station, served at the time by the Baltimore and Ohio Railroad, played a brief but key role during John Brown's 1859 raid on the Federal Armory in nearby Harpers Ferry, Virginia (since 1863, West Virginia).

The conductor stopped the train and sent a message about the abolitionist rebellion to B&O headquarters.

After confirming it, the Railroad notified President James Buchanan, Virginia Governor Henry A.