Who wrote the Phantom Stallion series and how many books are there?

Terri Farley from Southern California authored the Phantom Stallion series about a girl named Samantha "Sam" Forster who shares a unique bond with a wild horse called The Phantom Stallion. The series comprises 24 books:

The Wild One - (July 2002)
Mustang Moon - (2002)
Dark Sunshine - (October 2002)
The Renegade - (November 2002)
Free Again - (January 2003)
The Challenger - (March 2003)
Desert Dancer - (May 2003)
Golden Ghost - (July 2003)
Gift Horse - (October 2003)
Red Feather Filly - (February 2004)
Untamed - (April 2004)
Rain Dance - (July 2004)
Heartbreak Bronco - (October 2004)
Moonrise - (February 2005)
Kidnapped Colt - (April 2005)
The Wildest Heart - (June 2005)
Mountain Mare - (September 2005)
Firefly - (October 2005)
Secret Star - (January 2006)
Blue Wings - (February 2006)
Dawn Runner - (May 2006)
Wild Honey - (July 2006)
Gypsy Gold - (September 2006)
Run Away Home - (December 2006)

Here is a link to it's Wiki page. Lists all characters & books in the series:

https://en.wikipedia.org/wiki/The_Phantom_Stallion#Novels_in_the_series