2008: Good Masters! Sweet Ladies! Voices from a Medieval Village, by Laura Amy Schlitz - set in 1255 in an English manor village.Have I missed any books? It looks like more realistic medieval settings (and darker stories in general) have been especially popular in the last ten years. Before that, fantasy settings - Ye Merry Old England, or the Middle Ages as we like to imagine they might have been - (like in the tales of Robin Hood) were more popular.
2004: The Tale of Despereaux: Being the Story of a Mouse, a Princess, Some Soup, and a Spool of Thread, by Kate DiCamillo - ok, this is fantasy, but it's set in a castle with a dungeon, and there's a princess.
2003: Crispin: The Cross of Lead, by Avi - set in England in the 1300's.
2002: A Single Shard, by Linda Sue Park - an exception to the usual "merry olde England" setting, since this story is set in 12th century Korea - but the village society and feudal structure are very similar.
1996: The Midwife's Apprentice, by Karen Cushman - another English village in the 1300's.
1987: The Whipping Boy, by Sid Fleischman - like Despereaux, this is set in a fantasy world of castles, villages, and fairs.
1985: The Hero and the Crown, by Robin McKinley - set in a vaguely Arabic fantasy world, with castles and dragons.
1969: The High King by Lloyd Alexander - Prydain is not unlike medieval Europe.
1950: The Door in the Wall by Marguerite de Angeli - between 1350-1370, London and a castle on the Welsh border.
1943: Adam of the Road by Elizabeth Janet Gray - 1200's England - Oxford and several other cities.
1929: The Trumpeter of Krakow by Eric P. Kelly - medieval Poland instead of England!
1924: The Dark Frigate by Charles Hawes - set partially in England in the 1600's, but the inns and blacksmiths and the like are very similar to those in stories set a few centuries earlier.
I do love reading about the past in these books, it's been one of my favorite things about this project. Good thing I like it so much, because historical fiction is apparently really popular amongst Newbery Committee members.