The barns at Wolf Trap were originally for cattle.  The bell-roofed barn in particular was designed as a "modern" dairy facility, with its silo, milking facilities, and huge hayloft. 

In the 1970's, the barns became stables for thoroughbred race horses, which were raised on the farm, and for hunter/jumpers (which is what one does with a race horse that is no longer winning).  

The barns were run down and empty when the farm changed hands in 2004.  They received extensive repairs and were put back in service.  They have been rented to various trainers and equine professionals over the past decade.  They are currently rented and operated by Gleann Oighrig, LLC, which is owned by Martha Mitchell, M.D.

The following is from the Gleann Oighrig Facebook page:

"We focus on breeding, training, competing, and sales of Appaloosas, Knabstruppers, and other more traditional Warmblood horses for dressage and eventing."

Never heard of a Knabstrupper?  The following is from the website of the American Knabstrupper Association:

About the Knabstrupper

Believed to have originated from the pre-history spotted horses of the region of Europe now known as Spain, the Knabstrupper is one of the oldest breed registries in Europe. Established in 1812, the Knabstrupper started with a single chestnut blanketed mare purchased by a Danish butcher named Flaeb from a Spanish cavalry officer. The mare, who became known as FLAEBEHOPPEN (which literally means “Flaeb’s mare), was purchased by Major Villars Lunn who owned an estate called “Knabstrupgaard” in Holbaek, Nordsealand, Denmark.

Flaeb’s mare was bred to a Fredricksborg stallion and produced a wildly colored stallion son who was named Flaebehingsten. Between the two of them, Flaebehoppen and Flaebehingsten were bred to a large variety of good quality horses, producing loudly colored offspring and grand offspring and establishing the Knabstrupper horses as some of the most sought after in Europe at that time.