There are 6 books in the The North American Woman Trilogy series. The newest book is And One Rode West which came out in 1992.

2
A Pirate's Pleasure

Book cover of A Pirate's Pleasure
He took the proud vixen as his prisoner and swore she would serve . . . 

She was his defiant captive.

With her flame gold-hair and azure eyes, Skye Kinsdale was a prize beyond compare. Betrothed to a lord she'd never met, she set sail for America sworn to reject…

3
Love Not a Rebel

Book cover of Love Not a Rebel
He vowed to conquer her in every way. But she swore to Love Not a Rebel.
 
They called her “Highness,” ravishing Lady Amanda Sterling, forced to spy on Lord Eric Cameron by the lord governor of Virginia and her evil, ambitious father. She’d detested Eric Cameron on sight. He was…

4
One Wore Blue

Book cover of One Wore Blue
Kiernan Miller is the perfect Southern belle, all velvet and silk and spun-gold hair. She could never imagine her idyllic plantation life changing. Even as war brews, she dreams of the embrace of her neighbor, the devastatingly handsome Jesse Cameron--who returns her desire, kiss by tempestuous kiss. But he has…

5
And One Wore Gray

And One Wore Gray
The sequel to One Wore Blue follows Jesse Cameron's brother Daniel, a Confederate colonel, whose love for Callie Michaelson, fierce Union supporter, threatens their lives and forces them to face terrible decisions. Originally in paperback.

6
And One Rode West

And One Rode West
Love conquers all in Heather Graham’s Civil War series, as a delicate love—born from the bitter aftermath of war—is destined to bloom on the untamed frontier.
 
As the dust settles in the South, Christa Cameron emerges from the Confederacy’s bitter defeat bent but not broken, her spirit unvanquished, and her…