Night of Shadows by Ed Gorman (1990)
Before the turn of the last century, a woman named Anna Placak became the first uniformed female police officer in Cedar Rapids, Iowa, and, perhaps, in the world. The real-life Anna Placak became the inspiration for Ed Gorman's Anna Toland, the detective in Night of Shadows, as well as in several short stories by Gorman.
Anna, a widow, is a police matron, favored by the chief of police and desired by police detective David Peary. She has some distinctly modern ideas for 1895 and hopes to move beyond be a matron to becoming an actual constable. She has studied the latest police methods and investigative techniques but is having a hard time convincing others of their worth.
Although this is an age of electricity and telephones (and stories of the possibility of flying machines!), Cedar Rapids is straddled between the days of the old west and modern times. When it is learned that notorious gunslinger Stephen Fuller is returning to his home town to pay his respects to a dying boyhood friend, plans are made to make his visit as peaceful as possible. Fuller is known to have a hair trigger when drinking and has left at least a dozen bodies behind to back up that reputation. Anna is assigned to keep the gunfighter out of trouble. Fuller, however, is old and tired and doesn't want trouble but a drunk with a secret past tries to goad him. Fuller settles the argument with his fist rather than his gun. Embarrassed, the drunk tries to shoot Fuller down on a lonely street later that night. Before either could fire, the drunk is shot in the back by someone else and Fuller is accused of the crime.
Anna is convinced that Fuller is innocent. What no one realizes is that Cedar Rapids also harbors a grotesque serial killer who has remained hidden from sight by his doting mother.
As with any Gorman novel, there are twists and turns and surprises. It's a fast-paced ride with more than its share of thrills and a (dare I use the adverb?) lovingly portrayed historical look at Cedar Rapids and the times. But the heart of the book is Anna and the challenges facing her as a woman -- challenges from her colleagues and from the mind-set of the times as well as challenges from her own self-doubts. The thread that Anna weaves throughout the story adds a dimension to this book, transcending it from a good novel to a must-read.