I saw the following posted on the bulletin board at my local farmer's co-op in Warrenton, VA today:

WANTED
By the United States Park Police

The United States Park Police is seeking horses that need a job for Mounted Police Work. The patrol horse must be sound and a minimum of 15.3 hands, preferably 16 hands or taller, and be able to walk, trot and canter. We accept all breeds and colors but no stallions. Call the Mounted Unit at – (202) 426-6853, (202) 905-1682 cell or email Officer Mariea Clowers at Mariea_Clowers@nps.gov to find out more information.

Link to ad:
http://www.nps.gov/uspp/HorWan12.pdf