Wagons West: Colorado (original 1981; edition 2011)

DENVER! Braving the Rockies and hte untamed wilderness, they come to the wild frontier town and watched it explode into a city of fabulous instant wealth. Some were desperate men and women fleeing the mounting turbulence in the East. Others were adventurers forsaking the played-out dreams of the California gold fields.
They were lured by the most powerful promise of all - bonanza!

As the guns of Civil War rumble, a fledgling nation stands on the brink of disaster.
General Lee Blake stakes his life on the biggest challenge of his career - Colorado, a raw, awesome land with vast, new-found wealth must remain part of the Union. 
Aiding him in his mission is Luke Brandon, a mineral expert masquerading as a banker, whose young wife years for riches of her own. And Cathy Blake, who is threatened by a voluptuous rival for her husband's heart, is forced to summon all the fire in her blood to fight for her man.