Some historical detective fiction series ideas
Note some are vastly superior to others! A couple are contemporary and therefore reflect attitudes of their times. My definition of a series is three or more books featuring the same character(s)
Pre-Tudor
Paul Doherty - Brother Athelstan (1300s)
Ellis Peters - Cadfael (1100s Shrewsbury)
Elizabethan
Fiona Buckley - Ursula Blanchard
P F Chisholm - Sir Robert Carey (Cumbria/Northumberland)
Edward Marston - Nicholas Bracewell
S J Parris - Giordano Bruno
S W Perry - Nicholas Shelby
C J Sansom - Shardlake
Restoration
Edward Marston - Christopher Redmayne
Andrew Taylor - James Marwood & Cat Lovett
Georgian
Douglas Skelton - Jonas Flynt (late 1700s)
Chris Nickson - Simon Westow (1820s Leeds)
Victorian
Anna Katharine Green - Mr Gryce, Amelia Butterworth (contemporary, American, very melodramatic writing style)
Chris Nickson - Tom Harper (Leeds)
Ambrose Parry - Raven & Fisher (Edinburgh)
Edwardian/WWI
Edward Marston - Home Front
Jacqueline Winspear - Maisie Dobbs
1920s
Cora Harrison - Reverend Mother (Cork)
1930s
Margery Allingham - Albert Campion (contemporary)
Elizabeth Daly - Henry Gamage (contemporary New York/East Coast USA)
C H B Kitchin - Malcolm Warren (contemporary)
E C R Lorac - Macdonald, Rivers (contemporary with particular warning for antisemitism. Even when sympathetic to the character her words can be quite hard to take)
Patricia Wentworth - Miss Silver (contemporary, late 1920s thru to early 1960s)
1960s
Patricia Hall - Kate O'Donnell
1980s
Sue Grafton - A to Z