The Marlborough Horse Trials

Rosaryville State Park, Upper Marlboro, Maryland

The only USEA recognized event east of I-95 and a small town eventing gem.

The Marlborough Horse Trials are sanctioned by the United States Eventing Association (USEA) and United States Equestrian Federation (USEF). Together, these organizations establish standards for competition in the U.S. and oversee the development of the sport, preparing riders to represent the U.S. at the Olympics and other world-class events.

Get In Touch

USEA Recognized Horse Trials 

September 12th, 2026

Rosaryville State Park

USEA Omnibus
Entry Link Coming Soon

  • Coming soon

  • Dressage Tests:

    T: 2026 USEA Training Test A

    N: 2026 USEF Novice Test A

    BN: 2026 USEA Beginner Novice Test A

    S: 2026 USEA Starter Test A

    Arenas and warm-up on level grass.

  • Coming soon

  • Erin Gilmore Photography

  • Address: 7700 W. Marlton Dr, Upper Marlboro, MD 20772, USA

    Park entrance is on Marlton Road West off Rt. 301 South. It is not on Rosaryville Road! From South: I-95 to MD, Rt. 4 east to US Rt. 301 south 4 miles to Rosaryville State Park. Entrance is on the right just after Rt 301 crosses Osborne Road (Exxon station and 7-11 store on the right at Osborne and Rt 301). From North: I-97 to MD Rt 3 south becomes MD Rt 301 south. Same as above. Once you enter the park via W. Marlton Road (from Route 301 North), drive back a short distance, turn right at the fork and continue back to event parking (on your right and left as you enter the large clearing). There will be directional signs on the day of an event and there is also a small island with state park signs at the forked turn. If you miss the turn and go straight, do not panic. This exit will put you back on Route 301 North. It will then be necessary to do a U-Turn and come back to the first entrance. Please note the entrance and exit are One-Way only for your safety. For map and directions see our web site:

  • Coming soon

Volunteer at Marlborough Horse Trials

Each year, MHT requires approximately 100 volunteers to host a successful horse trial.

Volunteer Sign Up

We need YOU!

Marlborough Horse Trials is a non-profit organization, and your support is greatly appreciated by the MHT Board, horses, riders, and all those who enjoy the beauty of Rosaryville State Park year-round!

For questions or to sign up as a volunteer, please visit the links under “Volunteer Sign-Ups” or email MHTvolunteer@gmail.com

  • Sign up here

  • Jobs available include:

    • Cross Country Jump Judge

    • Dressage Steward

    • Dressage Scribe

    • Show Jumping Steward

    • Show Jumping Crew

  • MHT also requires extensive help before and after the event with:

    • Routine maintenance of Rosaryville Park

    • Cross Country Course Decorations

    • Dressage Ring Set-up/Take-down

    • Show Jumping Set-up/Take-down