Phantom Stallion
by Jessica
(Virginia, USA)
These are a really great series of books that everyone should read!
The Wild One:
Sam's father has good reason to send her away from his Nevada ranch to a San Francisco aunt. Sam was seriously injured when she fell from a young stallion named Blackie; she was struck by Blackie's hoof in a cloud of confusion and dust, and Blackie has been missing ever since.