P. B. Ryan published six Gilded Age mysteries between 2003 and 2007. That may be all in the series, since it ended at a good stopping point and there haven't been any since 2007.
In order, the books are Still Life with Murder, Murder in a Mill Town, Death on Beacon Hill, Murder on Black Friday, Murder in the North End, and A Bucket of Ashes. The main character was Nell Sweeney, who grows up very poor and in an abusive family near Cape Cod. When the series opens, she is a nurse to a doctor who four years earlier saved her life and has been her friend and teacher since. From him she learns not just nursing skills, but literature, language, and more. They are called to a difficult birth of a maidservant in the Cape Cod summer mansion of the wealthy Boston Brahmin Hewitt faimily. The child, a girl, is born safely. The mother is married, but her husband has been away in the Army during the Civil War for too long for it to be his child. Viola Hewitt, the family matron, has had four boys herself and decides to adopt the baby girl. She likes what she sees of Nell, and persuades her to enter her emplay as nurse and later governess to little Grace. It is too good an opportunity for Nell to pass up. The Hewitt family believes that both its older sons, Will and Robbie, died at the notorious Andersonville prisoner of war camp. When Grace is about three, they find out that Will survived, but is now charged with murder and is an opium addict. The addiction was due to his wounding at Andersonville and the painful months it took him to escape North. Nell solves his murder and the two become fast friends.and together go on to solve other murders.
The books are well written. For the most part the plots and characters are believeable. The characters develop in satisfying ways. If I have any quarrel with the books it is that Nell is constantly talking about how she must portect her reputation, or lose her job, which means losing Gracie, the most important person in her life - and yet she is always doing things to put that reputation in jeopardy, and making enemies whom one would guess would tattle on her. She is fired once by the family patriarch but Viola forces him to rehire her. It is a fairly minor quibble in an otherwise highly enjoyable series.