The Last Twelve Miles by Erika Robuck

Two real, brilliant women on opposite sides of the law, in a deadly game of cat and mouse…

1926. Washington, D.C.

The Coast Guard is losing the Prohibition Rum War, but they have a new, secret weapon to crack smuggler codes, intercept traffic, and destroy the rum trade one skiff at a time. That secret weapon is a 5'2" mastermind in heels, who also happens to be a wife and mother: Mrs. Elizebeth Smith Friedman, one half of the husband-and-wife pair who invented cryptanalysis. 

Bahamas

Cleo Lythogoe, The Bahama Queen, announces her retirement while regaling the thugs at the bar with tales of murder and mayhem on the high seas. Marie Waite, listening in, knows an opportunity when she hears it, and she wants the crown for herself so badly she can taste it. So begins Marie's plan to rise as rumrunner royalty long enough to get her family in the black. But the more sophisticated her operation grows, the more she appears on the radar of the feds.

Meanwhile, Elizebeth is the only codebreaker battling scores of smugglers. Despite the strain of solving thousands of intercepted messages, traveling the country, and testifying in court, Elizabeth's work becomes personal—especially when she discovers the identity of her premier adversary is the notorious Marie Waite. 

From the glamorous world of D.C. Intelligence to the sultry shores of the Straits of Florida, The Last Twelve Miles is based on the true story of two women masterminds trying to outwit each other in a dangerous and fascinating high stakes game.